// SPDX-License-Identifier: GPL-2.0-only
/*
 *
 * Copyright (C) 2011 Novell Inc.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fileattr.h>
#include <linux/splice.h>
#include <linux/xattr.h>
#include <linux/security.h>
#include <linux/uaccess.h>
#include <linux/sched/signal.h>
#include <linux/cred.h>
#include <linux/namei.h>
#include <linux/ratelimit.h>
#include <linux/exportfs.h>
#include "overlayfs.h"

#define OVL_COPY_UP_CHUNK_SIZE (1 << 20)

static int ovl_ccup_set(const char *buf, const struct kernel_param *param)
{
        pr_warn("\"check_copy_up\" module option is obsolete\n");
        return 0;
}

static int ovl_ccup_get(char *buf, const struct kernel_param *param)
{
        return sprintf(buf, "N\n");
}

module_param_call(check_copy_up, ovl_ccup_set, ovl_ccup_get, NULL, 0644);
MODULE_PARM_DESC(check_copy_up, "Obsolete; does nothing");

static bool ovl_must_copy_xattr(const char *name)
{
        return !strcmp(name, XATTR_POSIX_ACL_ACCESS) ||
               !strcmp(name, XATTR_POSIX_ACL_DEFAULT) ||
               !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN);
}

static int ovl_copy_acl(struct ovl_fs *ofs, const struct path *path,
                        struct dentry *dentry, const char *acl_name)
{
        int err;
        struct posix_acl *clone, *real_acl = NULL;

        real_acl = ovl_get_acl_path(path, acl_name, false);
        if (!real_acl)
                return 0;

        if (IS_ERR(real_acl)) {
                err = PTR_ERR(real_acl);
                if (err == -ENODATA || err == -EOPNOTSUPP)
                        return 0;
                return err;
        }

        clone = posix_acl_clone(real_acl, GFP_KERNEL);
        posix_acl_release(real_acl); /* release original acl */
        if (!clone)
                return -ENOMEM;

        err = ovl_do_set_acl(ofs, dentry, acl_name, clone);

        /* release cloned acl */
        posix_acl_release(clone);
        return err;
}

int ovl_copy_xattr(struct super_block *sb, const struct path *oldpath, struct dentry *new)
{
        struct dentry *old = oldpath->dentry;
        ssize_t list_size, size, value_size = 0;
        char *buf, *name, *value = NULL;
        int error = 0;
        size_t slen;

        if (!old->d_inode->i_op->listxattr || !new->d_inode->i_op->listxattr)
                return 0;

        list_size = vfs_listxattr(old, NULL, 0);
        if (list_size <= 0) {
                if (list_size == -EOPNOTSUPP)
                        return 0;
                return list_size;
        }

        buf = kvzalloc(list_size, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        list_size = vfs_listxattr(old, buf, list_size);
        if (list_size <= 0) {
                error = list_size;
                goto out;
        }

        for (name = buf; list_size; name += slen) {
                slen = strnlen(name, list_size) + 1;

                /* underlying fs providing us with an broken xattr list? */
                if (WARN_ON(slen > list_size)) {
                        error = -EIO;
                        break;
                }
                list_size -= slen;

                if (ovl_is_private_xattr(sb, name))
                        continue;

                error = security_inode_copy_up_xattr(old, name);
                if (error == -ECANCELED) {
                        error = 0;
                        continue; /* Discard */
                }
                if (error < 0 && error != -EOPNOTSUPP)
                        break;

                if (is_posix_acl_xattr(name)) {
                        error = ovl_copy_acl(OVL_FS(sb), oldpath, new, name);
                        if (!error)
                                continue;
                        /* POSIX ACLs must be copied. */
                        break;
                }

retry:
                size = ovl_do_getxattr(oldpath, name, value, value_size);
                if (size == -ERANGE)
                        size = ovl_do_getxattr(oldpath, name, NULL, 0);

                if (size < 0) {
                        error = size;
                        break;
                }

                if (size > value_size) {
                        void *new;

                        new = kvmalloc(size, GFP_KERNEL);
                        if (!new) {
                                error = -ENOMEM;
                                break;
                        }
                        kvfree(value);
                        value = new;
                        value_size = size;
                        goto retry;
                }

                error = ovl_do_setxattr(OVL_FS(sb), new, name, value, size, 0);
                if (error) {
                        if (error != -EOPNOTSUPP || ovl_must_copy_xattr(name))
                                break;

                        /* Ignore failure to copy unknown xattrs */
                        error = 0;
                }
        }
        kvfree(value);
out:
        kvfree(buf);
        return error;
}

static int ovl_copy_fileattr(struct inode *inode, const struct path *old,
                             const struct path *new)
{
        struct file_kattr oldfa = { .flags_valid = true };
        struct file_kattr newfa = { .flags_valid = true };
        int err;

        err = ovl_real_fileattr_get(old, &oldfa);
        if (err) {
                /* Ntfs-3g returns -EINVAL for "no fileattr support" */
                if (err == -ENOTTY || err == -EINVAL)
                        return 0;
                pr_warn("failed to retrieve lower fileattr (%pd2, err=%i)\n",
                        old->dentry, err);
                return err;
        }

        /*
         * We cannot set immutable and append-only flags on upper inode,
         * because we would not be able to link upper inode to upper dir
         * not set overlay private xattr on upper inode.
         * Store these flags in overlay.protattr xattr instead.
         */
        if (oldfa.flags & OVL_PROT_FS_FLAGS_MASK) {
                err = ovl_set_protattr(inode, new->dentry, &oldfa);
                if (err == -EPERM)
                        pr_warn_once("copying fileattr: no xattr on upper\n");
                else if (err)
                        return err;
        }

        /* Don't bother copying flags if none are set */
        if (!(oldfa.flags & OVL_COPY_FS_FLAGS_MASK))
                return 0;

        err = ovl_real_fileattr_get(new, &newfa);
        if (err) {
                /*
                 * Returning an error if upper doesn't support fileattr will
                 * result in a regression, so revert to the old behavior.
                 */
                if (err == -ENOTTY || err == -EINVAL) {
                        pr_warn_once("copying fileattr: no support on upper\n");
                        return 0;
                }
                pr_warn("failed to retrieve upper fileattr (%pd2, err=%i)\n",
                        new->dentry, err);
                return err;
        }

        BUILD_BUG_ON(OVL_COPY_FS_FLAGS_MASK & ~FS_COMMON_FL);
        newfa.flags &= ~OVL_COPY_FS_FLAGS_MASK;
        newfa.flags |= (oldfa.flags & OVL_COPY_FS_FLAGS_MASK);

        BUILD_BUG_ON(OVL_COPY_FSX_FLAGS_MASK & ~FS_XFLAG_COMMON);
        newfa.fsx_xflags &= ~OVL_COPY_FSX_FLAGS_MASK;
        newfa.fsx_xflags |= (oldfa.fsx_xflags & OVL_COPY_FSX_FLAGS_MASK);

        return ovl_real_fileattr_set(new, &newfa);
}

static int ovl_verify_area(loff_t pos, loff_t pos2, loff_t len, loff_t totlen)
{
        loff_t tmp;

        if (pos != pos2)
                return -EIO;
        if (pos < 0 || len < 0 || totlen < 0)
                return -EIO;
        if (check_add_overflow(pos, len, &tmp))
                return -EIO;
        return 0;
}

static int ovl_sync_file(const struct path *path)
{
        struct file *new_file;
        int err;

        new_file = ovl_path_open(path, O_LARGEFILE | O_RDONLY);
        if (IS_ERR(new_file))
                return PTR_ERR(new_file);

        err = vfs_fsync(new_file, 0);
        fput(new_file);

        return err;
}

static int ovl_copy_up_file(struct ovl_fs *ofs, struct dentry *dentry,
                            struct file *new_file, loff_t len,
                            bool datasync)
{
        struct path datapath;
        struct file *old_file;
        loff_t old_pos = 0;
        loff_t new_pos = 0;
        loff_t cloned;
        loff_t data_pos = -1;
        loff_t hole_len;
        bool skip_hole = false;
        int error = 0;

        ovl_path_lowerdata(dentry, &datapath);
        if (WARN_ON_ONCE(datapath.dentry == NULL) ||
            WARN_ON_ONCE(len < 0))
                return -EIO;

        old_file = ovl_path_open(&datapath, O_LARGEFILE | O_RDONLY);
        if (IS_ERR(old_file))
                return PTR_ERR(old_file);

        /* Try to use clone_file_range to clone up within the same fs */
        cloned = vfs_clone_file_range(old_file, 0, new_file, 0, len, 0);
        if (cloned == len)
                goto out_fput;

        /* Couldn't clone, so now we try to copy the data */
        error = rw_verify_area(READ, old_file, &old_pos, len);
        if (!error)
                error = rw_verify_area(WRITE, new_file, &new_pos, len);
        if (error)
                goto out_fput;

        /* Check if lower fs supports seek operation */
        if (old_file->f_mode & FMODE_LSEEK)
                skip_hole = true;

        while (len) {
                size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
                ssize_t bytes;

                if (len < this_len)
                        this_len = len;

                if (signal_pending_state(TASK_KILLABLE, current)) {
                        error = -EINTR;
                        break;
                }

                /*
                 * Fill zero for hole will cost unnecessary disk space
                 * and meanwhile slow down the copy-up speed, so we do
                 * an optimization for hole during copy-up, it relies
                 * on SEEK_DATA implementation in lower fs so if lower
                 * fs does not support it, copy-up will behave as before.
                 *
                 * Detail logic of hole detection as below:
                 * When we detect next data position is larger than current
                 * position we will skip that hole, otherwise we copy
                 * data in the size of OVL_COPY_UP_CHUNK_SIZE. Actually,
                 * it may not recognize all kind of holes and sometimes
                 * only skips partial of hole area. However, it will be
                 * enough for most of the use cases.
                 *
                 * We do not hold upper sb_writers throughout the loop to avert
                 * lockdep warning with llseek of lower file in nested overlay:
                 * - upper sb_writers
                 * -- lower ovl_inode_lock (ovl_llseek)
                 */
                if (skip_hole && data_pos < old_pos) {
                        data_pos = vfs_llseek(old_file, old_pos, SEEK_DATA);
                        if (data_pos > old_pos) {
                                hole_len = data_pos - old_pos;
                                len -= hole_len;
                                old_pos = new_pos = data_pos;
                                continue;
                        } else if (data_pos == -ENXIO) {
                                break;
                        } else if (data_pos < 0) {
                                skip_hole = false;
                        }
                }

                error = ovl_verify_area(old_pos, new_pos, this_len, len);
                if (error)
                        break;

                bytes = do_splice_direct(old_file, &old_pos,
                                         new_file, &new_pos,
                                         this_len, SPLICE_F_MOVE);
                if (bytes <= 0) {
                        error = bytes;
                        break;
                }
                WARN_ON(old_pos != new_pos);

                len -= bytes;
        }
        /* call fsync once, either now or later along with metadata */
        if (!error && ovl_should_sync(ofs) && datasync)
                error = vfs_fsync(new_file, 0);
out_fput:
        fput(old_file);
        return error;
}

static int ovl_set_size(struct ovl_fs *ofs,
                        struct dentry *upperdentry, struct kstat *stat)
{
        struct iattr attr = {
                .ia_valid = ATTR_SIZE,
                .ia_size = stat->size,
        };

        return ovl_do_notify_change(ofs, upperdentry, &attr);
}

static int ovl_set_timestamps(struct ovl_fs *ofs, struct dentry *upperdentry,
                              struct kstat *stat)
{
        struct iattr attr = {
                .ia_valid =
                     ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET | ATTR_CTIME,
                .ia_atime = stat->atime,
                .ia_mtime = stat->mtime,
        };

        return ovl_do_notify_change(ofs, upperdentry, &attr);
}

int ovl_set_attr(struct ovl_fs *ofs, struct dentry *upperdentry,
                 struct kstat *stat)
{
        int err = 0;

        if (!S_ISLNK(stat->mode)) {
                struct iattr attr = {
                        .ia_valid = ATTR_MODE,
                        .ia_mode = stat->mode,
                };
                err = ovl_do_notify_change(ofs, upperdentry, &attr);
        }
        if (!err) {
                struct iattr attr = {
                        .ia_valid = ATTR_UID | ATTR_GID,
                        .ia_vfsuid = VFSUIDT_INIT(stat->uid),
                        .ia_vfsgid = VFSGIDT_INIT(stat->gid),
                };
                err = ovl_do_notify_change(ofs, upperdentry, &attr);
        }
        if (!err)
                ovl_set_timestamps(ofs, upperdentry, stat);

        return err;
}

struct ovl_fh *ovl_encode_real_fh(struct ovl_fs *ofs, struct inode *realinode,
                                  bool is_upper)
{
        struct ovl_fh *fh;
        int fh_type, dwords;
        int buflen = MAX_HANDLE_SZ;
        uuid_t *uuid = &realinode->i_sb->s_uuid;
        int err;

        /* Make sure the real fid stays 32bit aligned */
        BUILD_BUG_ON(OVL_FH_FID_OFFSET % 4);
        BUILD_BUG_ON(MAX_HANDLE_SZ + OVL_FH_FID_OFFSET > 255);

        fh = kzalloc(buflen + OVL_FH_FID_OFFSET, GFP_KERNEL);
        if (!fh)
                return ERR_PTR(-ENOMEM);

        /*
         * We encode a non-connectable file handle for non-dir, because we
         * only need to find the lower inode number and we don't want to pay
         * the price or reconnecting the dentry.
         */
        dwords = buflen >> 2;
        fh_type = exportfs_encode_inode_fh(realinode, (void *)fh->fb.fid,
                                           &dwords, NULL, 0);
        buflen = (dwords << 2);

        err = -EIO;
        if (fh_type < 0 || fh_type == FILEID_INVALID ||
            WARN_ON(buflen > MAX_HANDLE_SZ))
                goto out_err;

        fh->fb.version = OVL_FH_VERSION;
        fh->fb.magic = OVL_FH_MAGIC;
        fh->fb.type = fh_type;
        fh->fb.flags = OVL_FH_FLAG_CPU_ENDIAN;
        /*
         * When we will want to decode an overlay dentry from this handle
         * and all layers are on the same fs, if we get a disconncted real
         * dentry when we decode fid, the only way to tell if we should assign
         * it to upperdentry or to lowerstack is by checking this flag.
         */
        if (is_upper)
                fh->fb.flags |= OVL_FH_FLAG_PATH_UPPER;
        fh->fb.len = sizeof(fh->fb) + buflen;
        if (ovl_origin_uuid(ofs))
                fh->fb.uuid = *uuid;

        return fh;

out_err:
        kfree(fh);
        return ERR_PTR(err);
}

struct ovl_fh *ovl_get_origin_fh(struct ovl_fs *ofs, struct dentry *origin)
{
        /*
         * When lower layer doesn't support export operations store a 'null' fh,
         * so we can use the overlay.origin xattr to distignuish between a copy
         * up and a pure upper inode.
         */
        if (!ovl_can_decode_fh(origin->d_sb))
                return NULL;

        return ovl_encode_real_fh(ofs, d_inode(origin), false);
}

int ovl_set_origin_fh(struct ovl_fs *ofs, const struct ovl_fh *fh,
                      struct dentry *upper)
{
        int err;

        /*
         * Do not fail when upper doesn't support xattrs.
         */
        err = ovl_check_setxattr(ofs, upper, OVL_XATTR_ORIGIN, fh->buf,
                                 fh ? fh->fb.len : 0, 0);

        /* Ignore -EPERM from setting "user.*" on symlink/special */
        return err == -EPERM ? 0 : err;
}

/* Store file handle of @upper dir in @index dir entry */
static int ovl_set_upper_fh(struct ovl_fs *ofs, struct dentry *upper,
                            struct dentry *index)
{
        const struct ovl_fh *fh;
        int err;

        fh = ovl_encode_real_fh(ofs, d_inode(upper), true);
        if (IS_ERR(fh))
                return PTR_ERR(fh);

        err = ovl_setxattr(ofs, index, OVL_XATTR_UPPER, fh->buf, fh->fb.len);

        kfree(fh);
        return err;
}

/*
 * Create and install index entry.
 */
static int ovl_create_index(struct dentry *dentry, const struct ovl_fh *fh,
                            struct dentry *upper)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
        struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
        struct dentry *temp = NULL;
        struct renamedata rd = {};
        struct qstr name = { };
        int err;

        /*
         * For now this is only used for creating index entry for directories,
         * because non-dir are copied up directly to index and then hardlinked
         * to upper dir.
         *
         * TODO: implement create index for non-dir, so we can call it when
         * encoding file handle for non-dir in case index does not exist.
         */
        if (WARN_ON(!d_is_dir(dentry)))
                return -EIO;

        /* Directory not expected to be indexed before copy up */
        if (WARN_ON(ovl_test_flag(OVL_INDEX, d_inode(dentry))))
                return -EIO;

        err = ovl_get_index_name_fh(fh, &name);
        if (err)
                return err;

        temp = ovl_create_temp(ofs, indexdir, OVL_CATTR(S_IFDIR | 0));
        err = PTR_ERR(temp);
        if (IS_ERR(temp))
                goto free_name;

        err = ovl_set_upper_fh(ofs, upper, temp);
        if (err)
                goto out;

        rd.mnt_idmap = ovl_upper_mnt_idmap(ofs);
        rd.old_parent = indexdir;
        rd.new_parent = indexdir;
        err = start_renaming_dentry(&rd, 0, temp, &name);
        if (err)
                goto out;

        err = ovl_do_rename_rd(&rd);
        end_renaming(&rd);
out:
        if (err)
                ovl_cleanup(ofs, indexdir, temp);
        dput(temp);
free_name:
        kfree(name.name);
        return err;
}

struct ovl_copy_up_ctx {
        struct dentry *parent;
        struct dentry *dentry;
        struct path lowerpath;
        struct kstat stat;
        struct kstat pstat;
        const char *link;
        struct dentry *destdir;
        struct qstr destname;
        struct dentry *workdir;
        const struct ovl_fh *origin_fh;
        bool origin;
        bool indexed;
        bool metacopy;
        bool metacopy_digest;
        bool metadata_fsync;
};

static int ovl_link_up(struct ovl_copy_up_ctx *c)
{
        int err;
        struct dentry *upper;
        struct dentry *upperdir = ovl_dentry_upper(c->parent);
        struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
        struct inode *udir = d_inode(upperdir);

        ovl_start_write(c->dentry);

        /* Mark parent "impure" because it may now contain non-pure upper */
        err = ovl_set_impure(c->parent, upperdir);
        if (err)
                goto out;

        err = ovl_set_nlink_lower(c->dentry);
        if (err)
                goto out;

        upper = ovl_start_creating_upper(ofs, upperdir,
                                         &QSTR_LEN(c->dentry->d_name.name,
                                                   c->dentry->d_name.len));
        err = PTR_ERR(upper);
        if (!IS_ERR(upper)) {
                err = ovl_do_link(ofs, ovl_dentry_upper(c->dentry), udir, upper);

                if (!err) {
                        /* Restore timestamps on parent (best effort) */
                        ovl_set_timestamps(ofs, upperdir, &c->pstat);
                        ovl_dentry_set_upper_alias(c->dentry);
                        ovl_dentry_update_reval(c->dentry, upper);
                }
                end_creating(upper);
        }
        if (err)
                goto out;

        err = ovl_set_nlink_upper(c->dentry);

out:
        ovl_end_write(c->dentry);
        return err;
}

static int ovl_copy_up_data(struct ovl_copy_up_ctx *c, const struct path *temp)
{
        struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
        struct file *new_file;
        int err;

        if (!S_ISREG(c->stat.mode) || c->metacopy || !c->stat.size)
                return 0;

        new_file = ovl_path_open(temp, O_LARGEFILE | O_WRONLY);
        if (IS_ERR(new_file))
                return PTR_ERR(new_file);

        err = ovl_copy_up_file(ofs, c->dentry, new_file, c->stat.size,
                               !c->metadata_fsync);
        fput(new_file);

        return err;
}

static int ovl_copy_up_metadata(struct ovl_copy_up_ctx *c, struct dentry *temp)
{
        struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
        struct inode *inode = d_inode(c->dentry);
        struct path upperpath = { .mnt = ovl_upper_mnt(ofs), .dentry = temp };
        int err;

        err = ovl_copy_xattr(c->dentry->d_sb, &c->lowerpath, temp);
        if (err)
                return err;

        if (inode->i_flags & OVL_FATTR_I_FLAGS_MASK &&
            (S_ISREG(c->stat.mode) || S_ISDIR(c->stat.mode))) {
                /*
                 * Copy the fileattr inode flags that are the source of already
                 * copied i_flags
                 */
                err = ovl_copy_fileattr(inode, &c->lowerpath, &upperpath);
                if (err)
                        return err;
        }

        /*
         * Store identifier of lower inode in upper inode xattr to
         * allow lookup of the copy up origin inode.
         *
         * Don't set origin when we are breaking the association with a lower
         * hard link.
         */
        if (c->origin) {
                err = ovl_set_origin_fh(ofs, c->origin_fh, temp);
                if (err)
                        return err;
        }

        if (c->metacopy) {
                struct path lowerdatapath;
                struct ovl_metacopy metacopy_data = OVL_METACOPY_INIT;

                ovl_path_lowerdata(c->dentry, &lowerdatapath);
                if (WARN_ON_ONCE(lowerdatapath.dentry == NULL))
                        return -EIO;
                err = ovl_get_verity_digest(ofs, &lowerdatapath, &metacopy_data);
                if (err)
                        return err;

                if (metacopy_data.digest_algo)
                        c->metacopy_digest = true;

                err = ovl_set_metacopy_xattr(ofs, temp, &metacopy_data);
                if (err)
                        return err;
        }

        inode_lock(temp->d_inode);
        if (S_ISREG(c->stat.mode))
                err = ovl_set_size(ofs, temp, &c->stat);
        if (!err)
                err = ovl_set_attr(ofs, temp, &c->stat);
        inode_unlock(temp->d_inode);

        /* fsync metadata before moving it into upper dir */
        if (!err && ovl_should_sync(ofs) && c->metadata_fsync)
                err = ovl_sync_file(&upperpath);

        return err;
}

static const struct cred *ovl_prepare_copy_up_creds(struct dentry *dentry)
{
        struct cred *copy_up_cred = NULL;
        int err;

        err = security_inode_copy_up(dentry, &copy_up_cred);
        if (err < 0)
                return ERR_PTR(err);

        if (!copy_up_cred)
                return NULL;

        return override_creds(copy_up_cred);
}

static void ovl_revert_copy_up_creds(const struct cred *orig_cred)
{
        const struct cred *copy_up_cred;

        copy_up_cred = revert_creds(orig_cred);
        put_cred(copy_up_cred);
}

DEFINE_CLASS(copy_up_creds, const struct cred *,
             if (!IS_ERR_OR_NULL(_T)) ovl_revert_copy_up_creds(_T),
             ovl_prepare_copy_up_creds(dentry), struct dentry *dentry)

/*
 * Copyup using workdir to prepare temp file.  Used when copying up directories,
 * special files or when upper fs doesn't support O_TMPFILE.
 */
static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)
{
        struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
        struct inode *inode;
        struct path path = { .mnt = ovl_upper_mnt(ofs) };
        struct renamedata rd = {};
        struct dentry *temp;
        int err;
        struct ovl_cattr cattr = {
                /* Can't properly set mode on creation because of the umask */
                .mode = c->stat.mode & S_IFMT,
                .rdev = c->stat.rdev,
                .link = c->link
        };

        scoped_class(copy_up_creds, copy_up_creds, c->dentry) {
                if (IS_ERR(copy_up_creds))
                        return PTR_ERR(copy_up_creds);

                ovl_start_write(c->dentry);
                temp = ovl_create_temp(ofs, c->workdir, &cattr);
                ovl_end_write(c->dentry);
        }

        if (IS_ERR(temp))
                return PTR_ERR(temp);

        /*
         * Copy up data first and then xattrs. Writing data after
         * xattrs will remove security.capability xattr automatically.
         */
        path.dentry = temp;
        err = ovl_copy_up_data(c, &path);
        ovl_start_write(c->dentry);
        if (err)
                goto cleanup_unlocked;

        if (S_ISDIR(c->stat.mode) && c->indexed) {
                err = ovl_create_index(c->dentry, c->origin_fh, temp);
                if (err)
                        goto cleanup_unlocked;
        }

        /*
         * We cannot hold lock_rename() throughout this helper, because of
         * lock ordering with sb_writers, which shouldn't be held when calling
         * ovl_copy_up_data(), so lock workdir and destdir and make sure that
         * temp wasn't moved before copy up completion or cleanup.
         */
        rd.mnt_idmap = ovl_upper_mnt_idmap(ofs);
        rd.old_parent = c->workdir;
        rd.new_parent = c->destdir;
        rd.flags = 0;
        err = start_renaming_dentry(&rd, 0, temp,
                                    &QSTR_LEN(c->destname.name, c->destname.len));
        if (err) {
                /* temp or workdir moved underneath us? map to -EIO */
                err = -EIO;
        }
        if (err)
                goto cleanup_unlocked;

        err = ovl_copy_up_metadata(c, temp);
        if (!err)
                err = ovl_do_rename_rd(&rd);
        end_renaming(&rd);

        if (err)
                goto cleanup_unlocked;

        inode = d_inode(c->dentry);
        if (c->metacopy_digest)
                ovl_set_flag(OVL_HAS_DIGEST, inode);
        else
                ovl_clear_flag(OVL_HAS_DIGEST, inode);
        ovl_clear_flag(OVL_VERIFIED_DIGEST, inode);

        if (!c->metacopy)
                ovl_set_upperdata(inode);
        ovl_inode_update(inode, temp);
        if (S_ISDIR(inode->i_mode))
                ovl_set_flag(OVL_WHITEOUTS, inode);
out:
        ovl_end_write(c->dentry);

        return err;

cleanup_unlocked:
        ovl_cleanup(ofs, c->workdir, temp);
        dput(temp);
        goto out;
}

/* Copyup using O_TMPFILE which does not require cross dir locking */
static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c)
{
        struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
        struct inode *udir = d_inode(c->destdir);
        struct dentry *temp, *upper;
        struct file *tmpfile;
        int err;

        scoped_class(copy_up_creds, copy_up_creds, c->dentry) {
                if (IS_ERR(copy_up_creds))
                        return PTR_ERR(copy_up_creds);

                ovl_start_write(c->dentry);
                tmpfile = ovl_do_tmpfile(ofs, c->workdir, c->stat.mode);
                ovl_end_write(c->dentry);
        }

        if (IS_ERR(tmpfile))
                return PTR_ERR(tmpfile);

        temp = tmpfile->f_path.dentry;
        if (!c->metacopy && c->stat.size) {
                err = ovl_copy_up_file(ofs, c->dentry, tmpfile, c->stat.size,
                                       !c->metadata_fsync);
                if (err)
                        goto out_fput;
        }

        ovl_start_write(c->dentry);

        err = ovl_copy_up_metadata(c, temp);
        if (err)
                goto out;

        upper = ovl_start_creating_upper(ofs, c->destdir,
                                         &QSTR_LEN(c->destname.name,
                                                   c->destname.len));
        err = PTR_ERR(upper);
        if (!IS_ERR(upper)) {
                err = ovl_do_link(ofs, temp, udir, upper);
                end_creating(upper);
        }

        if (err)
                goto out;

        if (c->metacopy_digest)
                ovl_set_flag(OVL_HAS_DIGEST, d_inode(c->dentry));
        else
                ovl_clear_flag(OVL_HAS_DIGEST, d_inode(c->dentry));
        ovl_clear_flag(OVL_VERIFIED_DIGEST, d_inode(c->dentry));

        if (!c->metacopy)
                ovl_set_upperdata(d_inode(c->dentry));
        ovl_inode_update(d_inode(c->dentry), dget(temp));

out:
        ovl_end_write(c->dentry);
out_fput:
        fput(tmpfile);
        return err;
}

/*
 * Copy up a single dentry
 *
 * All renames start with copy up of source if necessary.  The actual
 * rename will only proceed once the copy up was successful.  Copy up uses
 * upper parent i_mutex for exclusion.  Since rename can change d_parent it
 * is possible that the copy up will lock the old parent.  At that point
 * the file will have already been copied up anyway.
 */
static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
{
        int err;
        struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
        struct dentry *origin = c->lowerpath.dentry;
        struct ovl_fh *fh = NULL;
        bool to_index = false;

        /*
         * Indexed non-dir is copied up directly to the index entry and then
         * hardlinked to upper dir. Indexed dir is copied up to indexdir,
         * then index entry is created and then copied up dir installed.
         * Copying dir up to indexdir instead of workdir simplifies locking.
         */
        if (ovl_need_index(c->dentry)) {
                c->indexed = true;
                if (S_ISDIR(c->stat.mode))
                        c->workdir = ovl_indexdir(c->dentry->d_sb);
                else
                        to_index = true;
        }

        if (S_ISDIR(c->stat.mode) || c->stat.nlink == 1 || to_index) {
                fh = ovl_get_origin_fh(ofs, origin);
                if (IS_ERR(fh))
                        return PTR_ERR(fh);

                /* origin_fh may be NULL */
                c->origin_fh = fh;
                c->origin = true;
        }

        if (to_index) {
                c->destdir = ovl_indexdir(c->dentry->d_sb);
                err = ovl_get_index_name(ofs, origin, &c->destname);
                if (err)
                        goto out_free_fh;
        } else if (WARN_ON(!c->parent)) {
                /* Disconnected dentry must be copied up to index dir */
                err = -EIO;
                goto out_free_fh;
        } else {
                /*
                 * c->dentry->d_name is stabilzed by ovl_copy_up_start(),
                 * because if we got here, it means that c->dentry has no upper
                 * alias and changing ->d_name means going through ovl_rename()
                 * that will call ovl_copy_up() on source and target dentry.
                 */
                c->destname = c->dentry->d_name;
                /*
                 * Mark parent "impure" because it may now contain non-pure
                 * upper
                 */
                ovl_start_write(c->dentry);
                err = ovl_set_impure(c->parent, c->destdir);
                ovl_end_write(c->dentry);
                if (err)
                        goto out_free_fh;
        }

        /* Should we copyup with O_TMPFILE or with workdir? */
        if (S_ISREG(c->stat.mode) && ofs->tmpfile)
                err = ovl_copy_up_tmpfile(c);
        else
                err = ovl_copy_up_workdir(c);
        if (err)
                goto out;

        if (c->indexed)
                ovl_set_flag(OVL_INDEX, d_inode(c->dentry));

        ovl_start_write(c->dentry);
        if (to_index) {
                /* Initialize nlink for copy up of disconnected dentry */
                err = ovl_set_nlink_upper(c->dentry);
        } else {
                struct inode *udir = d_inode(c->destdir);

                /* Restore timestamps on parent (best effort) */
                inode_lock(udir);
                ovl_set_timestamps(ofs, c->destdir, &c->pstat);
                inode_unlock(udir);

                ovl_dentry_set_upper_alias(c->dentry);
                ovl_dentry_update_reval(c->dentry, ovl_dentry_upper(c->dentry));
        }
        ovl_end_write(c->dentry);

out:
        if (to_index)
                kfree(c->destname.name);
out_free_fh:
        kfree(fh);
        return err;
}

static bool ovl_need_meta_copy_up(struct dentry *dentry, umode_t mode,
                                  int flags)
{
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);

        if (!ofs->config.metacopy)
                return false;

        if (!S_ISREG(mode))
                return false;

        if (flags && ((OPEN_FMODE(flags) & FMODE_WRITE) || (flags & O_TRUNC)))
                return false;

        /* Fall back to full copy if no fsverity on source data and we require verity */
        if (ofs->config.verity_mode == OVL_VERITY_REQUIRE) {
                struct path lowerdata;

                ovl_path_lowerdata(dentry, &lowerdata);

                if (WARN_ON_ONCE(lowerdata.dentry == NULL) ||
                    ovl_ensure_verity_loaded(&lowerdata) ||
                    !fsverity_active(d_inode(lowerdata.dentry))) {
                        return false;
                }
        }

        return true;
}

static ssize_t ovl_getxattr_value(const struct path *path, char *name, char **value)
{
        ssize_t res;
        char *buf;

        res = ovl_do_getxattr(path, name, NULL, 0);
        if (res == -ENODATA || res == -EOPNOTSUPP)
                res = 0;

        if (res > 0) {
                buf = kzalloc(res, GFP_KERNEL);
                if (!buf)
                        return -ENOMEM;

                res = ovl_do_getxattr(path, name, buf, res);
                if (res < 0)
                        kfree(buf);
                else
                        *value = buf;
        }
        return res;
}

/* Copy up data of an inode which was copied up metadata only in the past. */
static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
{
        struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
        struct path upperpath;
        int err;
        char *capability = NULL;
        ssize_t cap_size;

        ovl_path_upper(c->dentry, &upperpath);
        if (WARN_ON(upperpath.dentry == NULL))
                return -EIO;

        if (c->stat.size) {
                err = cap_size = ovl_getxattr_value(&upperpath, XATTR_NAME_CAPS,
                                                    &capability);
                if (cap_size < 0)
                        goto out;
        }

        err = ovl_copy_up_data(c, &upperpath);
        if (err)
                goto out_free;

        /*
         * Writing to upper file will clear security.capability xattr. We
         * don't want that to happen for normal copy-up operation.
         */
        ovl_start_write(c->dentry);
        if (capability) {
                err = ovl_do_setxattr(ofs, upperpath.dentry, XATTR_NAME_CAPS,
                                      capability, cap_size, 0);
        }
        if (!err) {
                err = ovl_removexattr(ofs, upperpath.dentry,
                                      OVL_XATTR_METACOPY);
        }
        ovl_end_write(c->dentry);
        if (err)
                goto out_free;

        ovl_clear_flag(OVL_HAS_DIGEST, d_inode(c->dentry));
        ovl_clear_flag(OVL_VERIFIED_DIGEST, d_inode(c->dentry));
        ovl_set_upperdata(d_inode(c->dentry));
out_free:
        kfree(capability);
out:
        return err;
}

static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
                           int flags)
{
        int err;
        DEFINE_DELAYED_CALL(done);
        struct path parentpath;
        struct ovl_copy_up_ctx ctx = {
                .parent = parent,
                .dentry = dentry,
                .workdir = ovl_workdir(dentry),
        };

        if (WARN_ON(!ctx.workdir))
                return -EROFS;

        ovl_path_lower(dentry, &ctx.lowerpath);
        err = vfs_getattr(&ctx.lowerpath, &ctx.stat,
                          STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
        if (err)
                return err;

        if (!kuid_has_mapping(current_user_ns(), ctx.stat.uid) ||
            !kgid_has_mapping(current_user_ns(), ctx.stat.gid))
                return -EOVERFLOW;

        /*
         * With "fsync=strict", we fsync after final metadata copyup, for
         * both regular files and directories to get atomic copyup semantics
         * on filesystems that do not use strict metadata ordering (e.g. ubifs).
         *
         * By default, we want to avoid fsync on all meta copyup, because
         * that will hurt performance of workloads such as chown -R, so we
         * only fsync on data copyup as legacy behavior.
         */
        ctx.metadata_fsync = ovl_should_sync_metadata(OVL_FS(dentry->d_sb)) &&
                             (S_ISREG(ctx.stat.mode) || S_ISDIR(ctx.stat.mode));
        ctx.metacopy = ovl_need_meta_copy_up(dentry, ctx.stat.mode, flags);

        if (parent) {
                ovl_path_upper(parent, &parentpath);
                ctx.destdir = parentpath.dentry;

                err = vfs_getattr(&parentpath, &ctx.pstat,
                                  STATX_ATIME | STATX_MTIME,
                                  AT_STATX_SYNC_AS_STAT);
                if (err)
                        return err;
        }

        /* maybe truncate regular file. this has no effect on dirs */
        if (flags & O_TRUNC)
                ctx.stat.size = 0;

        if (S_ISLNK(ctx.stat.mode)) {
                ctx.link = vfs_get_link(ctx.lowerpath.dentry, &done);
                if (IS_ERR(ctx.link))
                        return PTR_ERR(ctx.link);
        }

        err = ovl_copy_up_start(dentry, flags);
        /* err < 0: interrupted, err > 0: raced with another copy-up */
        if (unlikely(err)) {
                if (err > 0)
                        err = 0;
        } else {
                if (!ovl_dentry_upper(dentry))
                        err = ovl_do_copy_up(&ctx);
                if (!err && parent && !ovl_dentry_has_upper_alias(dentry))
                        err = ovl_link_up(&ctx);
                if (!err && ovl_dentry_needs_data_copy_up_locked(dentry, flags))
                        err = ovl_copy_up_meta_inode_data(&ctx);
                ovl_copy_up_end(dentry);
        }
        do_delayed_call(&done);

        return err;
}

static int ovl_copy_up_flags(struct dentry *dentry, int flags)
{
        int err = 0;
        bool disconnected = (dentry->d_flags & DCACHE_DISCONNECTED);

        /*
         * With NFS export, copy up can get called for a disconnected non-dir.
         * In this case, we will copy up lower inode to index dir without
         * linking it to upper dir.
         */
        if (WARN_ON(disconnected && d_is_dir(dentry)))
                return -EIO;

        /*
         * We may not need lowerdata if we are only doing metacopy up, but it is
         * not very important to optimize this case, so do lazy lowerdata lookup
         * before any copy up, so we can do it before taking ovl_inode_lock().
         */
        err = ovl_verify_lowerdata(dentry);
        if (err)
                return err;

        while (!err) {
                struct dentry *next;
                struct dentry *parent = NULL;

                if (ovl_already_copied_up(dentry, flags))
                        break;

                next = dget(dentry);
                /* find the topmost dentry not yet copied up */
                for (; !disconnected;) {
                        parent = dget_parent(next);

                        if (ovl_dentry_upper(parent))
                                break;

                        dput(next);
                        next = parent;
                }

                with_ovl_creds(dentry->d_sb)
                        err = ovl_copy_up_one(parent, next, flags);

                dput(parent);
                dput(next);
        }

        return err;
}

static bool ovl_open_need_copy_up(struct dentry *dentry, int flags)
{
        /* Copy up of disconnected dentry does not set upper alias */
        if (ovl_already_copied_up(dentry, flags))
                return false;

        if (special_file(d_inode(dentry)->i_mode))
                return false;

        if (!ovl_open_flags_need_copy_up(flags))
                return false;

        return true;
}

int ovl_maybe_copy_up(struct dentry *dentry, int flags)
{
        if (!ovl_open_need_copy_up(dentry, flags))
                return 0;

        return ovl_copy_up_flags(dentry, flags);
}

int ovl_copy_up_with_data(struct dentry *dentry)
{
        return ovl_copy_up_flags(dentry, O_WRONLY);
}

int ovl_copy_up(struct dentry *dentry)
{
        return ovl_copy_up_flags(dentry, 0);
}