// SPDX-License-Identifier: GPL-2.0
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/freezer.h>
#include <linux/mm.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/swap.h>
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/pagemap.h>
#include <linux/perf_event.h>
#include <linux/highmem.h>
#include <linux/spinlock.h>
#include <linux/key.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/coredump.h>
#include <linux/sort.h>
#include <linux/sched/coredump.h>
#include <linux/sched/signal.h>
#include <linux/sched/task_stack.h>
#include <linux/utsname.h>
#include <linux/pid_namespace.h>
#include <linux/module.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/tsacct_kern.h>
#include <linux/cn_proc.h>
#include <linux/audit.h>
#include <linux/kmod.h>
#include <linux/fsnotify.h>
#include <linux/fs_struct.h>
#include <linux/pipe_fs_i.h>
#include <linux/oom.h>
#include <linux/compat.h>
#include <linux/fs.h>
#include <linux/path.h>
#include <linux/timekeeping.h>
#include <linux/sysctl.h>
#include <linux/elf.h>
#include <linux/pidfs.h>
#include <linux/net.h>
#include <linux/socket.h>
#include <net/af_unix.h>
#include <net/net_namespace.h>
#include <net/sock.h>
#include <uapi/linux/pidfd.h>
#include <uapi/linux/un.h>
#include <uapi/linux/coredump.h>

#include <linux/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/tlb.h>
#include <asm/exec.h>

#include <trace/events/task.h>
#include "internal.h"

#include <trace/events/sched.h>

static bool dump_vma_snapshot(struct coredump_params *cprm);
static void free_vma_snapshot(struct coredump_params *cprm);

#define CORE_FILE_NOTE_SIZE_DEFAULT (4*1024*1024)
/* Define a reasonable max cap */
#define CORE_FILE_NOTE_SIZE_MAX (16*1024*1024)
/*
 * File descriptor number for the pidfd for the thread-group leader of
 * the coredumping task installed into the usermode helper's file
 * descriptor table.
 */
#define COREDUMP_PIDFD_NUMBER 3

static int core_uses_pid;
static unsigned int core_pipe_limit;
static unsigned int core_sort_vma;
static char core_pattern[CORENAME_MAX_SIZE] = "core";
static int core_name_size = CORENAME_MAX_SIZE;
unsigned int core_file_note_size_limit = CORE_FILE_NOTE_SIZE_DEFAULT;
static atomic_t core_pipe_count = ATOMIC_INIT(0);

enum coredump_type_t {
        COREDUMP_FILE           = 1,
        COREDUMP_PIPE           = 2,
        COREDUMP_SOCK           = 3,
        COREDUMP_SOCK_REQ       = 4,
};

struct core_name {
        char *corename __counted_by_ptr(size);
        int used, size;
        unsigned int core_pipe_limit;
        bool core_dumped;
        enum coredump_type_t core_type;
        u64 mask;
};

static int expand_corename(struct core_name *cn, int size)
{
        char *corename;

        size = kmalloc_size_roundup(size);
        corename = krealloc(cn->corename, size, GFP_KERNEL);
        if (!corename)
                return -ENOMEM;

        cn->corename = corename;
        cn->size = size;

        if (size > core_name_size) /* racy but harmless */
                core_name_size = size;

        return 0;
}

static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
                                     va_list arg)
{
        int free, need;
        va_list arg_copy;

again:
        free = cn->size - cn->used;

        va_copy(arg_copy, arg);
        need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
        va_end(arg_copy);

        if (need < free) {
                cn->used += need;
                return 0;
        }

        if (!expand_corename(cn, cn->size + need - free + 1))
                goto again;

        return -ENOMEM;
}

static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
{
        va_list arg;
        int ret;

        va_start(arg, fmt);
        ret = cn_vprintf(cn, fmt, arg);
        va_end(arg);

        return ret;
}

static __printf(2, 3)
int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
{
        int cur = cn->used;
        va_list arg;
        int ret;

        va_start(arg, fmt);
        ret = cn_vprintf(cn, fmt, arg);
        va_end(arg);

        if (ret == 0) {
                /*
                 * Ensure that this coredump name component can't cause the
                 * resulting corefile path to consist of a ".." or ".".
                 */
                if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
                                (cn->used - cur == 2 && cn->corename[cur] == '.'
                                && cn->corename[cur+1] == '.'))
                        cn->corename[cur] = '!';

                /*
                 * Empty names are fishy and could be used to create a "//" in a
                 * corefile name, causing the coredump to happen one directory
                 * level too high. Enforce that all components of the core
                 * pattern are at least one character long.
                 */
                if (cn->used == cur)
                        ret = cn_printf(cn, "!");
        }

        for (; cur < cn->used; ++cur) {
                if (cn->corename[cur] == '/')
                        cn->corename[cur] = '!';
        }
        return ret;
}

static int cn_print_exe_file(struct core_name *cn, bool name_only)
{
        struct file *exe_file;
        char *pathbuf, *path, *ptr;
        int ret;

        exe_file = get_mm_exe_file(current->mm);
        if (!exe_file)
                return cn_esc_printf(cn, "%s (path unknown)", current->comm);

        pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
        if (!pathbuf) {
                ret = -ENOMEM;
                goto put_exe_file;
        }

        path = file_path(exe_file, pathbuf, PATH_MAX);
        if (IS_ERR(path)) {
                ret = PTR_ERR(path);
                goto free_buf;
        }

        if (name_only) {
                ptr = strrchr(path, '/');
                if (ptr)
                        path = ptr + 1;
        }
        ret = cn_esc_printf(cn, "%s", path);

free_buf:
        kfree(pathbuf);
put_exe_file:
        fput(exe_file);
        return ret;
}

/*
 * coredump_parse will inspect the pattern parameter, and output a name
 * into corename, which must have space for at least CORENAME_MAX_SIZE
 * bytes plus one byte for the zero terminator.
 */
static bool coredump_parse(struct core_name *cn, struct coredump_params *cprm,
                           size_t **argv, int *argc)
{
        const struct cred *cred = current_cred();
        const char *pat_ptr = core_pattern;
        bool was_space = false;
        int pid_in_pattern = 0;
        int err = 0;

        cn->mask = COREDUMP_KERNEL;
        if (core_pipe_limit)
                cn->mask |= COREDUMP_WAIT;
        cn->used = 0;
        cn->corename = NULL;
        cn->core_pipe_limit = 0;
        cn->core_dumped = false;
        if (*pat_ptr == '|')
                cn->core_type = COREDUMP_PIPE;
        else if (*pat_ptr == '@')
                cn->core_type = COREDUMP_SOCK;
        else
                cn->core_type = COREDUMP_FILE;
        if (expand_corename(cn, core_name_size))
                return false;
        cn->corename[0] = '\0';

        switch (cn->core_type) {
        case COREDUMP_PIPE: {
                int argvs = sizeof(core_pattern) / 2;
                (*argv) = kmalloc_objs(**argv, argvs);
                if (!(*argv))
                        return false;
                (*argv)[(*argc)++] = 0;
                ++pat_ptr;
                if (!(*pat_ptr))
                        return false;
                break;
        }
        case COREDUMP_SOCK: {
                /* skip the @ */
                pat_ptr++;
                if (!(*pat_ptr))
                        return false;
                if (*pat_ptr == '@') {
                        pat_ptr++;
                        if (!(*pat_ptr))
                                return false;

                        cn->core_type = COREDUMP_SOCK_REQ;
                }

                err = cn_printf(cn, "%s", pat_ptr);
                if (err)
                        return false;

                /* Require absolute paths. */
                if (cn->corename[0] != '/')
                        return false;

                /*
                 * Ensure we can uses spaces to indicate additional
                 * parameters in the future.
                 */
                if (strchr(cn->corename, ' ')) {
                        coredump_report_failure("Coredump socket may not %s contain spaces", cn->corename);
                        return false;
                }

                /* Must not contain ".." in the path. */
                if (name_contains_dotdot(cn->corename)) {
                        coredump_report_failure("Coredump socket may not %s contain '..' spaces", cn->corename);
                        return false;
                }

                if (strlen(cn->corename) >= UNIX_PATH_MAX) {
                        coredump_report_failure("Coredump socket path %s too long", cn->corename);
                        return false;
                }

                /*
                 * Currently no need to parse any other options.
                 * Relevant information can be retrieved from the peer
                 * pidfd retrievable via SO_PEERPIDFD by the receiver or
                 * via /proc/<pid>, using the SO_PEERPIDFD to guard
                 * against pid recycling when opening /proc/<pid>.
                 */
                return true;
        }
        case COREDUMP_FILE:
                break;
        default:
                WARN_ON_ONCE(true);
                return false;
        }

        /* Repeat as long as we have more pattern to process and more output
           space */
        while (*pat_ptr) {
                /*
                 * Split on spaces before doing template expansion so that
                 * %e and %E don't get split if they have spaces in them
                 */
                if (cn->core_type == COREDUMP_PIPE) {
                        if (isspace(*pat_ptr)) {
                                if (cn->used != 0)
                                        was_space = true;
                                pat_ptr++;
                                continue;
                        } else if (was_space) {
                                was_space = false;
                                err = cn_printf(cn, "%c", '\0');
                                if (err)
                                        return false;
                                (*argv)[(*argc)++] = cn->used;
                        }
                }
                if (*pat_ptr != '%') {
                        err = cn_printf(cn, "%c", *pat_ptr++);
                } else {
                        switch (*++pat_ptr) {
                        /* single % at the end, drop that */
                        case 0:
                                goto out;
                        /* Double percent, output one percent */
                        case '%':
                                err = cn_printf(cn, "%c", '%');
                                break;
                        /* pid */
                        case 'p':
                                pid_in_pattern = 1;
                                err = cn_printf(cn, "%d",
                                              task_tgid_vnr(current));
                                break;
                        /* global pid */
                        case 'P':
                                err = cn_printf(cn, "%d",
                                              task_tgid_nr(current));
                                break;
                        case 'i':
                                err = cn_printf(cn, "%d",
                                              task_pid_vnr(current));
                                break;
                        case 'I':
                                err = cn_printf(cn, "%d",
                                              task_pid_nr(current));
                                break;
                        /* uid */
                        case 'u':
                                err = cn_printf(cn, "%u",
                                                from_kuid(&init_user_ns,
                                                          cred->uid));
                                break;
                        /* gid */
                        case 'g':
                                err = cn_printf(cn, "%u",
                                                from_kgid(&init_user_ns,
                                                          cred->gid));
                                break;
                        case 'd':
                                err = cn_printf(cn, "%d",
                                        __get_dumpable(cprm->mm_flags));
                                break;
                        /* signal that caused the coredump */
                        case 's':
                                err = cn_printf(cn, "%d",
                                                cprm->siginfo->si_signo);
                                break;
                        /* UNIX time of coredump */
                        case 't': {
                                time64_t time;

                                time = ktime_get_real_seconds();
                                err = cn_printf(cn, "%lld", time);
                                break;
                        }
                        /* hostname */
                        case 'h':
                                down_read(&uts_sem);
                                err = cn_esc_printf(cn, "%s",
                                              utsname()->nodename);
                                up_read(&uts_sem);
                                break;
                        /* executable, could be changed by prctl PR_SET_NAME etc */
                        case 'e':
                                err = cn_esc_printf(cn, "%s", current->comm);
                                break;
                        /* file name of executable */
                        case 'f':
                                err = cn_print_exe_file(cn, true);
                                break;
                        case 'E':
                                err = cn_print_exe_file(cn, false);
                                break;
                        /* core limit size */
                        case 'c':
                                err = cn_printf(cn, "%lu",
                                              rlimit(RLIMIT_CORE));
                                break;
                        /* CPU the task ran on */
                        case 'C':
                                err = cn_printf(cn, "%d", cprm->cpu);
                                break;
                        /* pidfd number */
                        case 'F': {
                                /*
                                 * Installing a pidfd only makes sense if
                                 * we actually spawn a usermode helper.
                                 */
                                if (cn->core_type != COREDUMP_PIPE)
                                        break;

                                /*
                                 * Note that we'll install a pidfd for the
                                 * thread-group leader. We know that task
                                 * linkage hasn't been removed yet and even if
                                 * this @current isn't the actual thread-group
                                 * leader we know that the thread-group leader
                                 * cannot be reaped until @current has exited.
                                 */
                                cprm->pid = task_tgid(current);
                                err = cn_printf(cn, "%d", COREDUMP_PIDFD_NUMBER);
                                break;
                        }
                        default:
                                break;
                        }
                        ++pat_ptr;
                }

                if (err)
                        return false;
        }

out:
        /* Backward compatibility with core_uses_pid:
         *
         * If core_pattern does not include a %p (as is the default)
         * and core_uses_pid is set, then .%pid will be appended to
         * the filename. Do not do this for piped commands. */
        if (cn->core_type == COREDUMP_FILE && !pid_in_pattern && core_uses_pid)
                return cn_printf(cn, ".%d", task_tgid_vnr(current)) == 0;

        return true;
}

static int zap_process(struct signal_struct *signal, int exit_code)
{
        struct task_struct *t;
        int nr = 0;

        signal->flags = SIGNAL_GROUP_EXIT;
        signal->group_exit_code = exit_code;
        signal->group_stop_count = 0;

        __for_each_thread(signal, t) {
                task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
                if (t != current && !(t->flags & PF_POSTCOREDUMP)) {
                        sigaddset(&t->pending.signal, SIGKILL);
                        signal_wake_up(t, 1);
                        nr++;
                }
        }

        return nr;
}

static int zap_threads(struct task_struct *tsk,
                        struct core_state *core_state, int exit_code)
{
        struct signal_struct *signal = tsk->signal;
        int nr = -EAGAIN;

        spin_lock_irq(&tsk->sighand->siglock);
        if (!(signal->flags & SIGNAL_GROUP_EXIT) && !signal->group_exec_task) {
                /* Allow SIGKILL, see prepare_signal() */
                signal->core_state = core_state;
                nr = zap_process(signal, exit_code);
                clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
                tsk->flags |= PF_DUMPCORE;
                atomic_set(&core_state->nr_threads, nr);
        }
        spin_unlock_irq(&tsk->sighand->siglock);
        return nr;
}

static int coredump_wait(int exit_code, struct core_state *core_state)
{
        struct task_struct *tsk = current;
        int core_waiters = -EBUSY;

        init_completion(&core_state->startup);
        core_state->dumper.task = tsk;
        core_state->dumper.next = NULL;

        core_waiters = zap_threads(tsk, core_state, exit_code);
        if (core_waiters > 0) {
                struct core_thread *ptr;

                wait_for_completion_state(&core_state->startup,
                                          TASK_UNINTERRUPTIBLE|TASK_FREEZABLE);
                /*
                 * Wait for all the threads to become inactive, so that
                 * all the thread context (extended register state, like
                 * fpu etc) gets copied to the memory.
                 */
                ptr = core_state->dumper.next;
                while (ptr != NULL) {
                        wait_task_inactive(ptr->task, TASK_ANY);
                        ptr = ptr->next;
                }
        }

        return core_waiters;
}

static void coredump_finish(bool core_dumped)
{
        struct core_thread *curr, *next;
        struct task_struct *task;

        spin_lock_irq(&current->sighand->siglock);
        if (core_dumped && !__fatal_signal_pending(current))
                current->signal->group_exit_code |= 0x80;
        next = current->signal->core_state->dumper.next;
        current->signal->core_state = NULL;
        spin_unlock_irq(&current->sighand->siglock);

        while ((curr = next) != NULL) {
                next = curr->next;
                task = curr->task;
                /*
                 * see coredump_task_exit(), curr->task must not see
                 * ->task == NULL before we read ->next.
                 */
                smp_mb();
                curr->task = NULL;
                wake_up_process(task);
        }
}

static bool dump_interrupted(void)
{
        /*
         * SIGKILL or freezing() interrupt the coredumping. Perhaps we
         * can do try_to_freeze() and check __fatal_signal_pending(),
         * but then we need to teach dump_write() to restart and clear
         * TIF_SIGPENDING.
         */
        return fatal_signal_pending(current) || freezing(current);
}

static void wait_for_dump_helpers(struct file *file)
{
        struct pipe_inode_info *pipe = file->private_data;

        pipe_lock(pipe);
        pipe->readers++;
        pipe->writers--;
        wake_up_interruptible_sync(&pipe->rd_wait);
        kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
        pipe_unlock(pipe);

        /*
         * We actually want wait_event_freezable() but then we need
         * to clear TIF_SIGPENDING and improve dump_interrupted().
         */
        wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);

        pipe_lock(pipe);
        pipe->readers--;
        pipe->writers++;
        pipe_unlock(pipe);
}

/*
 * umh_coredump_setup
 * helper function to customize the process used
 * to collect the core in userspace.  Specifically
 * it sets up a pipe and installs it as fd 0 (stdin)
 * for the process.  Returns 0 on success, or
 * PTR_ERR on failure.
 * Note that it also sets the core limit to 1.  This
 * is a special value that we use to trap recursive
 * core dumps
 */
static int umh_coredump_setup(struct subprocess_info *info, struct cred *new)
{
        struct file *files[2];
        struct coredump_params *cp = (struct coredump_params *)info->data;
        int err;

        if (cp->pid) {
                struct file *pidfs_file __free(fput) = NULL;

                pidfs_file = pidfs_alloc_file(cp->pid, 0);
                if (IS_ERR(pidfs_file))
                        return PTR_ERR(pidfs_file);

                pidfs_coredump(cp);

                /*
                 * Usermode helpers are childen of either
                 * system_dfl_wq or of kthreadd. So we know that
                 * we're starting off with a clean file descriptor
                 * table. So we should always be able to use
                 * COREDUMP_PIDFD_NUMBER as our file descriptor value.
                 */
                err = replace_fd(COREDUMP_PIDFD_NUMBER, pidfs_file, 0);
                if (err < 0)
                        return err;
        }

        err = create_pipe_files(files, 0);
        if (err)
                return err;

        cp->file = files[1];

        err = replace_fd(0, files[0], 0);
        fput(files[0]);
        if (err < 0)
                return err;

        /* and disallow core files too */
        current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};

        return 0;
}

#ifdef CONFIG_UNIX
static bool coredump_sock_connect(struct core_name *cn, struct coredump_params *cprm)
{
        struct file *file __free(fput) = NULL;
        struct sockaddr_un addr = {
                .sun_family = AF_UNIX,
        };
        ssize_t addr_len;
        int retval;
        struct socket *socket;

        addr_len = strscpy(addr.sun_path, cn->corename);
        if (addr_len < 0)
                return false;
        addr_len += offsetof(struct sockaddr_un, sun_path) + 1;

        /*
         * It is possible that the userspace process which is supposed
         * to handle the coredump and is listening on the AF_UNIX socket
         * coredumps. Userspace should just mark itself non dumpable.
         */

        retval = sock_create_kern(&init_net, AF_UNIX, SOCK_STREAM, 0, &socket);
        if (retval < 0)
                return false;

        file = sock_alloc_file(socket, 0, NULL);
        if (IS_ERR(file))
                return false;

        /*
         * Set the thread-group leader pid which is used for the peer
         * credentials during connect() below. Then immediately register
         * it in pidfs...
         */
        cprm->pid = task_tgid(current);
        retval = pidfs_register_pid(cprm->pid);
        if (retval)
                return false;

        /*
         * ... and set the coredump information so userspace has it
         * available after connect()...
         */
        pidfs_coredump(cprm);

        retval = kernel_connect(socket, (struct sockaddr_unsized *)(&addr), addr_len,
                                O_NONBLOCK | SOCK_COREDUMP);

        if (retval) {
                if (retval == -EAGAIN)
                        coredump_report_failure("Coredump socket %s receive queue full", addr.sun_path);
                else
                        coredump_report_failure("Coredump socket connection %s failed %d", addr.sun_path, retval);
                return false;
        }

        /* ... and validate that @sk_peer_pid matches @cprm.pid. */
        if (WARN_ON_ONCE(unix_peer(socket->sk)->sk_peer_pid != cprm->pid))
                return false;

        cprm->limit = RLIM_INFINITY;
        cprm->file = no_free_ptr(file);

        return true;
}

static inline bool coredump_sock_recv(struct file *file, struct coredump_ack *ack, size_t size, int flags)
{
        struct msghdr msg = {};
        struct kvec iov = { .iov_base = ack, .iov_len = size };
        ssize_t ret;

        memset(ack, 0, size);
        ret = kernel_recvmsg(sock_from_file(file), &msg, &iov, 1, size, flags);
        return ret == size;
}

static inline bool coredump_sock_send(struct file *file, struct coredump_req *req)
{
        struct msghdr msg = { .msg_flags = MSG_NOSIGNAL };
        struct kvec iov = { .iov_base = req, .iov_len = sizeof(*req) };
        ssize_t ret;

        ret = kernel_sendmsg(sock_from_file(file), &msg, &iov, 1, sizeof(*req));
        return ret == sizeof(*req);
}

static_assert(sizeof(enum coredump_mark) == sizeof(__u32));

static inline bool coredump_sock_mark(struct file *file, enum coredump_mark mark)
{
        struct msghdr msg = { .msg_flags = MSG_NOSIGNAL };
        struct kvec iov = { .iov_base = &mark, .iov_len = sizeof(mark) };
        ssize_t ret;

        ret = kernel_sendmsg(sock_from_file(file), &msg, &iov, 1, sizeof(mark));
        return ret == sizeof(mark);
}

static inline void coredump_sock_wait(struct file *file)
{
        ssize_t n;

        /*
         * We use a simple read to wait for the coredump processing to
         * finish. Either the socket is closed or we get sent unexpected
         * data. In both cases, we're done.
         */
        n = __kernel_read(file, &(char){ 0 }, 1, NULL);
        if (n > 0)
                coredump_report_failure("Coredump socket had unexpected data");
        else if (n < 0)
                coredump_report_failure("Coredump socket failed");
}

static inline void coredump_sock_shutdown(struct file *file)
{
        struct socket *socket;

        socket = sock_from_file(file);
        if (!socket)
                return;

        /* Let userspace know we're done processing the coredump. */
        kernel_sock_shutdown(socket, SHUT_WR);
}

static bool coredump_sock_request(struct core_name *cn, struct coredump_params *cprm)
{
        struct coredump_req req = {
                .size           = sizeof(struct coredump_req),
                .mask           = COREDUMP_KERNEL | COREDUMP_USERSPACE |
                                  COREDUMP_REJECT | COREDUMP_WAIT,
                .size_ack       = sizeof(struct coredump_ack),
        };
        struct coredump_ack ack = {};
        ssize_t usize;

        if (cn->core_type != COREDUMP_SOCK_REQ)
                return true;

        /* Let userspace know what we support. */
        if (!coredump_sock_send(cprm->file, &req))
                return false;

        /* Peek the size of the coredump_ack. */
        if (!coredump_sock_recv(cprm->file, &ack, sizeof(ack.size),
                                MSG_PEEK | MSG_WAITALL))
                return false;

        /* Refuse unknown coredump_ack sizes. */
        usize = ack.size;
        if (usize < COREDUMP_ACK_SIZE_VER0) {
                coredump_sock_mark(cprm->file, COREDUMP_MARK_MINSIZE);
                return false;
        }

        if (usize > sizeof(ack)) {
                coredump_sock_mark(cprm->file, COREDUMP_MARK_MAXSIZE);
                return false;
        }

        /* Now retrieve the coredump_ack. */
        if (!coredump_sock_recv(cprm->file, &ack, usize, MSG_WAITALL))
                return false;
        if (ack.size != usize)
                return false;

        /* Refuse unknown coredump_ack flags. */
        if (ack.mask & ~req.mask) {
                coredump_sock_mark(cprm->file, COREDUMP_MARK_UNSUPPORTED);
                return false;
        }

        /* Refuse mutually exclusive options. */
        if (hweight64(ack.mask & (COREDUMP_USERSPACE | COREDUMP_KERNEL |
                                  COREDUMP_REJECT)) != 1) {
                coredump_sock_mark(cprm->file, COREDUMP_MARK_CONFLICTING);
                return false;
        }

        if (ack.spare) {
                coredump_sock_mark(cprm->file, COREDUMP_MARK_UNSUPPORTED);
                return false;
        }

        cn->mask = ack.mask;
        return coredump_sock_mark(cprm->file, COREDUMP_MARK_REQACK);
}

static bool coredump_socket(struct core_name *cn, struct coredump_params *cprm)
{
        if (!coredump_sock_connect(cn, cprm))
                return false;

        return coredump_sock_request(cn, cprm);
}
#else
static inline void coredump_sock_wait(struct file *file) { }
static inline void coredump_sock_shutdown(struct file *file) { }
static inline bool coredump_socket(struct core_name *cn, struct coredump_params *cprm) { return false; }
#endif

/* cprm->mm_flags contains a stable snapshot of dumpability flags. */
static inline bool coredump_force_suid_safe(const struct coredump_params *cprm)
{
        /* Require nonrelative corefile path and be extra careful. */
        return __get_dumpable(cprm->mm_flags) == SUID_DUMP_ROOT;
}

static bool coredump_file(struct core_name *cn, struct coredump_params *cprm,
                          const struct linux_binfmt *binfmt)
{
        struct mnt_idmap *idmap;
        struct inode *inode;
        struct file *file __free(fput) = NULL;
        int open_flags = O_CREAT | O_WRONLY | O_NOFOLLOW | O_LARGEFILE | O_EXCL;

        if (cprm->limit < binfmt->min_coredump)
                return false;

        if (coredump_force_suid_safe(cprm) && cn->corename[0] != '/') {
                coredump_report_failure("this process can only dump core to a fully qualified path, skipping core dump");
                return false;
        }

        /*
         * Unlink the file if it exists unless this is a SUID
         * binary - in that case, we're running around with root
         * privs and don't want to unlink another user's coredump.
         */
        if (!coredump_force_suid_safe(cprm)) {
                CLASS(filename_kernel, name)(cn->corename);
                /*
                 * If it doesn't exist, that's fine. If there's some
                 * other problem, we'll catch it at the filp_open().
                 */
                filename_unlinkat(AT_FDCWD, name);
        }

        /*
         * There is a race between unlinking and creating the
         * file, but if that causes an EEXIST here, that's
         * fine - another process raced with us while creating
         * the corefile, and the other process won. To userspace,
         * what matters is that at least one of the two processes
         * writes its coredump successfully, not which one.
         */
        if (coredump_force_suid_safe(cprm)) {
                /*
                 * Using user namespaces, normal user tasks can change
                 * their current->fs->root to point to arbitrary
                 * directories. Since the intention of the "only dump
                 * with a fully qualified path" rule is to control where
                 * coredumps may be placed using root privileges,
                 * current->fs->root must not be used. Instead, use the
                 * root directory of init_task.
                 */
                struct path root;

                task_lock(&init_task);
                get_fs_root(init_task.fs, &root);
                task_unlock(&init_task);
                file = file_open_root(&root, cn->corename, open_flags, 0600);
                path_put(&root);
        } else {
                file = filp_open(cn->corename, open_flags, 0600);
        }
        if (IS_ERR(file))
                return false;

        inode = file_inode(file);
        if (inode->i_nlink > 1)
                return false;
        if (d_unhashed(file->f_path.dentry))
                return false;
        /*
         * AK: actually i see no reason to not allow this for named
         * pipes etc, but keep the previous behaviour for now.
         */
        if (!S_ISREG(inode->i_mode))
                return false;
        /*
         * Don't dump core if the filesystem changed owner or mode
         * of the file during file creation. This is an issue when
         * a process dumps core while its cwd is e.g. on a vfat
         * filesystem.
         */
        idmap = file_mnt_idmap(file);
        if (!vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), current_fsuid())) {
                coredump_report_failure("Core dump to %s aborted: cannot preserve file owner", cn->corename);
                return false;
        }
        if ((inode->i_mode & 0677) != 0600) {
                coredump_report_failure("Core dump to %s aborted: cannot preserve file permissions", cn->corename);
                return false;
        }
        if (!(file->f_mode & FMODE_CAN_WRITE))
                return false;
        if (do_truncate(idmap, file->f_path.dentry, 0, 0, file))
                return false;

        cprm->file = no_free_ptr(file);
        return true;
}

static bool coredump_pipe(struct core_name *cn, struct coredump_params *cprm,
                          size_t *argv, int argc)
{
        int argi;
        char **helper_argv __free(kfree) = NULL;
        struct subprocess_info *sub_info;

        if (cprm->limit == 1) {
                /* See umh_coredump_setup() which sets RLIMIT_CORE = 1.
                 *
                 * Normally core limits are irrelevant to pipes, since
                 * we're not writing to the file system, but we use
                 * cprm.limit of 1 here as a special value, this is a
                 * consistent way to catch recursive crashes.
                 * We can still crash if the core_pattern binary sets
                 * RLIM_CORE = !1, but it runs as root, and can do
                 * lots of stupid things.
                 *
                 * Note that we use task_tgid_vnr here to grab the pid
                 * of the process group leader.  That way we get the
                 * right pid if a thread in a multi-threaded
                 * core_pattern process dies.
                 */
                coredump_report_failure("RLIMIT_CORE is set to 1, aborting core");
                return false;
        }
        cprm->limit = RLIM_INFINITY;

        cn->core_pipe_limit = atomic_inc_return(&core_pipe_count);
        if (core_pipe_limit && (core_pipe_limit < cn->core_pipe_limit)) {
                coredump_report_failure("over core_pipe_limit, skipping core dump");
                return false;
        }

        helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv), GFP_KERNEL);
        if (!helper_argv) {
                coredump_report_failure("%s failed to allocate memory", __func__);
                return false;
        }
        for (argi = 0; argi < argc; argi++)
                helper_argv[argi] = cn->corename + argv[argi];
        helper_argv[argi] = NULL;

        sub_info = call_usermodehelper_setup(helper_argv[0], helper_argv, NULL,
                                             GFP_KERNEL, umh_coredump_setup,
                                             NULL, cprm);
        if (!sub_info)
                return false;

        if (call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC)) {
                coredump_report_failure("|%s pipe failed", cn->corename);
                return false;
        }

        /*
         * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
         * have this set to NULL.
         */
        if (!cprm->file) {
                coredump_report_failure("Core dump to |%s disabled", cn->corename);
                return false;
        }

        return true;
}

static bool coredump_write(struct core_name *cn,
                          struct coredump_params *cprm,
                          const struct linux_binfmt *binfmt)
{

        if (dump_interrupted())
                return true;

        if (!dump_vma_snapshot(cprm))
                return false;

        file_start_write(cprm->file);
        cn->core_dumped = binfmt->core_dump(cprm);
        /*
         * Ensures that file size is big enough to contain the current
         * file postion. This prevents gdb from complaining about
         * a truncated file if the last "write" to the file was
         * dump_skip.
         */
        if (cprm->to_skip) {
                cprm->to_skip--;
                dump_emit(cprm, "", 1);
        }
        file_end_write(cprm->file);
        free_vma_snapshot(cprm);
        return true;
}

static void coredump_cleanup(struct core_name *cn, struct coredump_params *cprm)
{
        if (cprm->file)
                filp_close(cprm->file, NULL);
        if (cn->core_pipe_limit) {
                VFS_WARN_ON_ONCE(cn->core_type != COREDUMP_PIPE);
                atomic_dec(&core_pipe_count);
        }
        kfree(cn->corename);
        coredump_finish(cn->core_dumped);
}

static inline bool coredump_skip(const struct coredump_params *cprm,
                                 const struct linux_binfmt *binfmt)
{
        if (!binfmt)
                return true;
        if (!binfmt->core_dump)
                return true;
        if (!__get_dumpable(cprm->mm_flags))
                return true;
        return false;
}

static void do_coredump(struct core_name *cn, struct coredump_params *cprm,
                        size_t **argv, int *argc, const struct linux_binfmt *binfmt)
{
        if (!coredump_parse(cn, cprm, argv, argc)) {
                coredump_report_failure("format_corename failed, aborting core");
                return;
        }

        switch (cn->core_type) {
        case COREDUMP_FILE:
                if (!coredump_file(cn, cprm, binfmt))
                        return;
                break;
        case COREDUMP_PIPE:
                if (!coredump_pipe(cn, cprm, *argv, *argc))
                        return;
                break;
        case COREDUMP_SOCK_REQ:
                fallthrough;
        case COREDUMP_SOCK:
                if (!coredump_socket(cn, cprm))
                        return;
                break;
        default:
                WARN_ON_ONCE(true);
                return;
        }

        /* Don't even generate the coredump. */
        if (cn->mask & COREDUMP_REJECT)
                return;

        /* get us an unshared descriptor table; almost always a no-op */
        /* The cell spufs coredump code reads the file descriptor tables */
        if (unshare_files())
                return;

        if ((cn->mask & COREDUMP_KERNEL) && !coredump_write(cn, cprm, binfmt))
                return;

        coredump_sock_shutdown(cprm->file);

        /* Let the parent know that a coredump was generated. */
        if (cn->mask & COREDUMP_USERSPACE)
                cn->core_dumped = true;

        /*
         * When core_pipe_limit is set we wait for the coredump server
         * or usermodehelper to finish before exiting so it can e.g.,
         * inspect /proc/<pid>.
         */
        if (cn->mask & COREDUMP_WAIT) {
                switch (cn->core_type) {
                case COREDUMP_PIPE:
                        wait_for_dump_helpers(cprm->file);
                        break;
                case COREDUMP_SOCK_REQ:
                        fallthrough;
                case COREDUMP_SOCK:
                        coredump_sock_wait(cprm->file);
                        break;
                default:
                        break;
                }
        }
}

void vfs_coredump(const kernel_siginfo_t *siginfo)
{
        size_t *argv __free(kfree) = NULL;
        struct core_state core_state;
        struct core_name cn;
        const struct mm_struct *mm = current->mm;
        const struct linux_binfmt *binfmt = mm->binfmt;
        int argc = 0;
        struct coredump_params cprm = {
                .siginfo = siginfo,
                .limit = rlimit(RLIMIT_CORE),
                /*
                 * We must use the same mm->flags while dumping core to avoid
                 * inconsistency of bit flags, since this flag is not protected
                 * by any locks.
                 *
                 * Note that we only care about MMF_DUMP* flags.
                 */
                .mm_flags = __mm_flags_get_dumpable(mm),
                .vma_meta = NULL,
                .cpu = raw_smp_processor_id(),
        };

        audit_core_dumps(siginfo->si_signo);

        if (coredump_skip(&cprm, binfmt))
                return;

        CLASS(prepare_creds, cred)();
        if (!cred)
                return;
        /*
         * We cannot trust fsuid as being the "true" uid of the process
         * nor do we know its entire history. We only know it was tainted
         * so we dump it as root in mode 2, and only into a controlled
         * environment (pipe handler or fully qualified path).
         */
        if (coredump_force_suid_safe(&cprm))
                cred->fsuid = GLOBAL_ROOT_UID;

        if (coredump_wait(siginfo->si_signo, &core_state) < 0)
                return;

        scoped_with_creds(cred)
                do_coredump(&cn, &cprm, &argv, &argc, binfmt);
        coredump_cleanup(&cn, &cprm);
        return;
}

/*
 * Core dumping helper functions.  These are the only things you should
 * do on a core-file: use only these functions to write out all the
 * necessary info.
 */
static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
{
        struct file *file = cprm->file;
        loff_t pos = file->f_pos;
        ssize_t n;

        if (cprm->written + nr > cprm->limit)
                return 0;
        if (dump_interrupted())
                return 0;
        n = __kernel_write(file, addr, nr, &pos);
        if (n != nr)
                return 0;
        file->f_pos = pos;
        cprm->written += n;
        cprm->pos += n;

        return 1;
}

static int __dump_skip(struct coredump_params *cprm, size_t nr)
{
        static char zeroes[PAGE_SIZE];
        struct file *file = cprm->file;

        if (file->f_mode & FMODE_LSEEK) {
                if (dump_interrupted() || vfs_llseek(file, nr, SEEK_CUR) < 0)
                        return 0;
                cprm->pos += nr;
                return 1;
        }

        while (nr > PAGE_SIZE) {
                if (!__dump_emit(cprm, zeroes, PAGE_SIZE))
                        return 0;
                nr -= PAGE_SIZE;
        }

        return __dump_emit(cprm, zeroes, nr);
}

int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
{
        if (cprm->to_skip) {
                if (!__dump_skip(cprm, cprm->to_skip))
                        return 0;
                cprm->to_skip = 0;
        }
        return __dump_emit(cprm, addr, nr);
}
EXPORT_SYMBOL(dump_emit);

void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
{
        cprm->to_skip = pos - cprm->pos;
}
EXPORT_SYMBOL(dump_skip_to);

void dump_skip(struct coredump_params *cprm, size_t nr)
{
        cprm->to_skip += nr;
}
EXPORT_SYMBOL(dump_skip);

#ifdef CONFIG_ELF_CORE
static int dump_emit_page(struct coredump_params *cprm, struct page *page)
{
        struct bio_vec bvec;
        struct iov_iter iter;
        struct file *file = cprm->file;
        loff_t pos;
        ssize_t n;

        if (!page)
                return 0;

        if (cprm->to_skip) {
                if (!__dump_skip(cprm, cprm->to_skip))
                        return 0;
                cprm->to_skip = 0;
        }
        if (cprm->written + PAGE_SIZE > cprm->limit)
                return 0;
        if (dump_interrupted())
                return 0;
        pos = file->f_pos;
        bvec_set_page(&bvec, page, PAGE_SIZE, 0);
        iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE);
        n = __kernel_write_iter(cprm->file, &iter, &pos);
        if (n != PAGE_SIZE)
                return 0;
        file->f_pos = pos;
        cprm->written += PAGE_SIZE;
        cprm->pos += PAGE_SIZE;

        return 1;
}

/*
 * If we might get machine checks from kernel accesses during the
 * core dump, let's get those errors early rather than during the
 * IO. This is not performance-critical enough to warrant having
 * all the machine check logic in the iovec paths.
 */
#ifdef copy_mc_to_kernel

#define dump_page_alloc() alloc_page(GFP_KERNEL)
#define dump_page_free(x) __free_page(x)
static struct page *dump_page_copy(struct page *src, struct page *dst)
{
        void *buf = kmap_local_page(src);
        size_t left = copy_mc_to_kernel(page_address(dst), buf, PAGE_SIZE);
        kunmap_local(buf);
        return left ? NULL : dst;
}

#else

/* We just want to return non-NULL; it's never used. */
#define dump_page_alloc() ERR_PTR(-EINVAL)
#define dump_page_free(x) ((void)(x))
static inline struct page *dump_page_copy(struct page *src, struct page *dst)
{
        return src;
}
#endif

int dump_user_range(struct coredump_params *cprm, unsigned long start,
                    unsigned long len)
{
        unsigned long addr;
        struct page *dump_page;
        int locked, ret;

        dump_page = dump_page_alloc();
        if (!dump_page)
                return 0;

        ret = 0;
        locked = 0;
        for (addr = start; addr < start + len; addr += PAGE_SIZE) {
                struct page *page;

                if (!locked) {
                        if (mmap_read_lock_killable(current->mm))
                                goto out;
                        locked = 1;
                }

                /*
                 * To avoid having to allocate page tables for virtual address
                 * ranges that have never been used yet, and also to make it
                 * easy to generate sparse core files, use a helper that returns
                 * NULL when encountering an empty page table entry that would
                 * otherwise have been filled with the zero page.
                 */
                page = get_dump_page(addr, &locked);
                if (page) {
                        if (locked) {
                                mmap_read_unlock(current->mm);
                                locked = 0;
                        }
                        int stop = !dump_emit_page(cprm, dump_page_copy(page, dump_page));
                        put_page(page);
                        if (stop)
                                goto out;
                } else {
                        dump_skip(cprm, PAGE_SIZE);
                }

                if (dump_interrupted())
                        goto out;

                if (!need_resched())
                        continue;
                if (locked) {
                        mmap_read_unlock(current->mm);
                        locked = 0;
                }
                cond_resched();
        }
        ret = 1;
out:
        if (locked)
                mmap_read_unlock(current->mm);

        dump_page_free(dump_page);
        return ret;
}
#endif

int dump_align(struct coredump_params *cprm, int align)
{
        unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
        if (align & (align - 1))
                return 0;
        if (mod)
                cprm->to_skip += align - mod;
        return 1;
}
EXPORT_SYMBOL(dump_align);

#ifdef CONFIG_SYSCTL

void validate_coredump_safety(void)
{
        if (suid_dumpable == SUID_DUMP_ROOT &&
            core_pattern[0] != '/' && core_pattern[0] != '|' && core_pattern[0] != '@') {

                coredump_report_failure("Unsafe core_pattern used with fs.suid_dumpable=2: "
                        "pipe handler or fully qualified core dump path required. "
                        "Set kernel.core_pattern before fs.suid_dumpable.");
        }
}

static inline bool check_coredump_socket(void)
{
        const char *p;

        if (core_pattern[0] != '@')
                return true;

        /*
         * Coredump socket must be located in the initial mount
         * namespace. Don't give the impression that anything else is
         * supported right now.
         */
        if (current->nsproxy->mnt_ns != init_task.nsproxy->mnt_ns)
                return false;

        /* Must be an absolute path... */
        if (core_pattern[1] != '/') {
                /* ... or the socket request protocol... */
                if (core_pattern[1] != '@')
                        return false;
                /* ... and if so must be an absolute path. */
                if (core_pattern[2] != '/')
                        return false;
                p = &core_pattern[2];
        } else {
                p = &core_pattern[1];
        }

        /* The path obviously cannot exceed UNIX_PATH_MAX. */
        if (strlen(p) >= UNIX_PATH_MAX)
                return false;

        /* Must not contain ".." in the path. */
        if (name_contains_dotdot(core_pattern))
                return false;

        return true;
}

static int proc_dostring_coredump(const struct ctl_table *table, int write,
                  void *buffer, size_t *lenp, loff_t *ppos)
{
        int error;
        ssize_t retval;
        char old_core_pattern[CORENAME_MAX_SIZE];

        if (!write)
                return proc_dostring(table, write, buffer, lenp, ppos);

        retval = strscpy(old_core_pattern, core_pattern, CORENAME_MAX_SIZE);

        error = proc_dostring(table, write, buffer, lenp, ppos);
        if (error)
                return error;

        if (!check_coredump_socket()) {
                strscpy(core_pattern, old_core_pattern, retval + 1);
                return -EINVAL;
        }

        validate_coredump_safety();
        return error;
}

static const unsigned int core_file_note_size_min = CORE_FILE_NOTE_SIZE_DEFAULT;
static const unsigned int core_file_note_size_max = CORE_FILE_NOTE_SIZE_MAX;
static char core_modes[] = {
        "file\npipe"
#ifdef CONFIG_UNIX
        "\nsocket"
#endif
};

static const struct ctl_table coredump_sysctls[] = {
        {
                .procname       = "core_uses_pid",
                .data           = &core_uses_pid,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
        {
                .procname       = "core_pattern",
                .data           = core_pattern,
                .maxlen         = CORENAME_MAX_SIZE,
                .mode           = 0644,
                .proc_handler   = proc_dostring_coredump,
        },
        {
                .procname       = "core_pipe_limit",
                .data           = &core_pipe_limit,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = SYSCTL_ZERO,
                .extra2         = SYSCTL_INT_MAX,
        },
        {
                .procname       = "core_file_note_size_limit",
                .data           = &core_file_note_size_limit,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_douintvec_minmax,
                .extra1         = (unsigned int *)&core_file_note_size_min,
                .extra2         = (unsigned int *)&core_file_note_size_max,
        },
        {
                .procname       = "core_sort_vma",
                .data           = &core_sort_vma,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_douintvec_minmax,
                .extra1         = SYSCTL_ZERO,
                .extra2         = SYSCTL_ONE,
        },
        {
                .procname       = "core_modes",
                .data           = core_modes,
                .maxlen         = sizeof(core_modes) - 1,
                .mode           = 0444,
                .proc_handler   = proc_dostring,
        },
};

static int __init init_fs_coredump_sysctls(void)
{
        register_sysctl_init("kernel", coredump_sysctls);
        return 0;
}
fs_initcall(init_fs_coredump_sysctls);
#endif /* CONFIG_SYSCTL */

/*
 * The purpose of always_dump_vma() is to make sure that special kernel mappings
 * that are useful for post-mortem analysis are included in every core dump.
 * In that way we ensure that the core dump is fully interpretable later
 * without matching up the same kernel and hardware config to see what PC values
 * meant. These special mappings include - vDSO, vsyscall, and other
 * architecture specific mappings
 */
static bool always_dump_vma(struct vm_area_struct *vma)
{
        /* Any vsyscall mappings? */
        if (vma == get_gate_vma(vma->vm_mm))
                return true;

        /*
         * Assume that all vmas with a .name op should always be dumped.
         * If this changes, a new vm_ops field can easily be added.
         */
        if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
                return true;

        /*
         * arch_vma_name() returns non-NULL for special architecture mappings,
         * such as vDSO sections.
         */
        if (arch_vma_name(vma))
                return true;

        return false;
}

#define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1

/*
 * Decide how much of @vma's contents should be included in a core dump.
 */
static unsigned long vma_dump_size(struct vm_area_struct *vma,
                                   unsigned long mm_flags)
{
#define FILTER(type)    (mm_flags & (1UL << MMF_DUMP_##type))

        /* always dump the vdso and vsyscall sections */
        if (always_dump_vma(vma))
                goto whole;

        if (vma->vm_flags & VM_DONTDUMP)
                return 0;

        /* support for DAX */
        if (vma_is_dax(vma)) {
                if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
                        goto whole;
                if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
                        goto whole;
                return 0;
        }

        /* Hugetlb memory check */
        if (is_vm_hugetlb_page(vma)) {
                if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
                        goto whole;
                if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
                        goto whole;
                return 0;
        }

        /* Do not dump I/O mapped devices or special mappings */
        if (vma->vm_flags & VM_IO)
                return 0;

        /* By default, dump shared memory if mapped from an anonymous file. */
        if (vma->vm_flags & VM_SHARED) {
                if (file_inode(vma->vm_file)->i_nlink == 0 ?
                    FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
                        goto whole;
                return 0;
        }

        /* Dump segments that have been written to.  */
        if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
                goto whole;
        if (vma->vm_file == NULL)
                return 0;

        if (FILTER(MAPPED_PRIVATE))
                goto whole;

        /*
         * If this is the beginning of an executable file mapping,
         * dump the first page to aid in determining what was mapped here.
         */
        if (FILTER(ELF_HEADERS) &&
            vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
                if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
                        return PAGE_SIZE;

                /*
                 * ELF libraries aren't always executable.
                 * We'll want to check whether the mapping starts with the ELF
                 * magic, but not now - we're holding the mmap lock,
                 * so copy_from_user() doesn't work here.
                 * Use a placeholder instead, and fix it up later in
                 * dump_vma_snapshot().
                 */
                return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER;
        }

#undef  FILTER

        return 0;

whole:
        return vma->vm_end - vma->vm_start;
}

/*
 * Helper function for iterating across a vma list.  It ensures that the caller
 * will visit `gate_vma' prior to terminating the search.
 */
static struct vm_area_struct *coredump_next_vma(struct vma_iterator *vmi,
                                       struct vm_area_struct *vma,
                                       struct vm_area_struct *gate_vma)
{
        if (gate_vma && (vma == gate_vma))
                return NULL;

        vma = vma_next(vmi);
        if (vma)
                return vma;
        return gate_vma;
}

static void free_vma_snapshot(struct coredump_params *cprm)
{
        if (cprm->vma_meta) {
                int i;
                for (i = 0; i < cprm->vma_count; i++) {
                        struct file *file = cprm->vma_meta[i].file;
                        if (file)
                                fput(file);
                }
                kvfree(cprm->vma_meta);
                cprm->vma_meta = NULL;
        }
}

static int cmp_vma_size(const void *vma_meta_lhs_ptr, const void *vma_meta_rhs_ptr)
{
        const struct core_vma_metadata *vma_meta_lhs = vma_meta_lhs_ptr;
        const struct core_vma_metadata *vma_meta_rhs = vma_meta_rhs_ptr;

        if (vma_meta_lhs->dump_size < vma_meta_rhs->dump_size)
                return -1;
        if (vma_meta_lhs->dump_size > vma_meta_rhs->dump_size)
                return 1;
        return 0;
}

/*
 * Under the mmap_lock, take a snapshot of relevant information about the task's
 * VMAs.
 */
static bool dump_vma_snapshot(struct coredump_params *cprm)
{
        struct vm_area_struct *gate_vma, *vma = NULL;
        struct mm_struct *mm = current->mm;
        VMA_ITERATOR(vmi, mm, 0);
        int i = 0;

        /*
         * Once the stack expansion code is fixed to not change VMA bounds
         * under mmap_lock in read mode, this can be changed to take the
         * mmap_lock in read mode.
         */
        if (mmap_write_lock_killable(mm))
                return false;

        cprm->vma_data_size = 0;
        gate_vma = get_gate_vma(mm);
        cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);

        cprm->vma_meta = kvmalloc_objs(*cprm->vma_meta, cprm->vma_count);
        if (!cprm->vma_meta) {
                mmap_write_unlock(mm);
                return false;
        }

        while ((vma = coredump_next_vma(&vmi, vma, gate_vma)) != NULL) {
                struct core_vma_metadata *m = cprm->vma_meta + i;

                m->start = vma->vm_start;
                m->end = vma->vm_end;
                m->flags = vma->vm_flags;
                m->dump_size = vma_dump_size(vma, cprm->mm_flags);
                m->pgoff = vma->vm_pgoff;
                m->file = vma->vm_file;
                if (m->file)
                        get_file(m->file);
                i++;
        }

        mmap_write_unlock(mm);

        for (i = 0; i < cprm->vma_count; i++) {
                struct core_vma_metadata *m = cprm->vma_meta + i;

                if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
                        char elfmag[SELFMAG];

                        if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) ||
                                        memcmp(elfmag, ELFMAG, SELFMAG) != 0) {
                                m->dump_size = 0;
                        } else {
                                m->dump_size = PAGE_SIZE;
                        }
                }

                cprm->vma_data_size += m->dump_size;
        }

        if (core_sort_vma)
                sort(cprm->vma_meta, cprm->vma_count, sizeof(*cprm->vma_meta),
                     cmp_vma_size, NULL);

        return true;
}