// SPDX-License-Identifier: GPL-2.0-only
/*
 * sysctl.c: General linux system control interface
 */

#include <linux/sysctl.h>
#include <linux/bitmap.h>
#include <linux/proc_fs.h>
#include <linux/ctype.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kobject.h>
#include <linux/highuid.h>
#include <linux/writeback.h>
#include <linux/initrd.h>
#include <linux/limits.h>
#include <linux/syscalls.h>
#include <linux/capability.h>

#include "../lib/kstrtox.h"

#include <linux/uaccess.h>
#include <asm/processor.h>

/* shared constants to be used in various sysctls */
const int sysctl_vals[] = { 0, 1, 2, 3, 4, 100, 200, 1000, 3000, INT_MAX, 65535, -1 };
EXPORT_SYMBOL(sysctl_vals);

const unsigned long sysctl_long_vals[] = { 0, 1, LONG_MAX };
EXPORT_SYMBOL_GPL(sysctl_long_vals);

#if defined(CONFIG_SYSCTL)

/* Constants used for minimum and maximum */
static const int ngroups_max = NGROUPS_MAX;
static const int cap_last_cap = CAP_LAST_CAP;

#ifdef CONFIG_PROC_SYSCTL

/**
 * enum sysctl_writes_mode - supported sysctl write modes
 *
 * @SYSCTL_WRITES_LEGACY: each write syscall must fully contain the sysctl value
 *      to be written, and multiple writes on the same sysctl file descriptor
 *      will rewrite the sysctl value, regardless of file position. No warning
 *      is issued when the initial position is not 0.
 * @SYSCTL_WRITES_WARN: same as above but warn when the initial file position is
 *      not 0.
 * @SYSCTL_WRITES_STRICT: writes to numeric sysctl entries must always be at
 *      file position 0 and the value must be fully contained in the buffer
 *      sent to the write syscall. If dealing with strings respect the file
 *      position, but restrict this to the max length of the buffer, anything
 *      passed the max length will be ignored. Multiple writes will append
 *      to the buffer.
 *
 * These write modes control how current file position affects the behavior of
 * updating internal kernel (SYSCTL_USER_TO_KERN) sysctl values through the proc
 * interface on each write.
 */
enum sysctl_writes_mode {
        SYSCTL_WRITES_LEGACY            = -1,
        SYSCTL_WRITES_WARN              = 0,
        SYSCTL_WRITES_STRICT            = 1,
};

static enum sysctl_writes_mode sysctl_writes_strict = SYSCTL_WRITES_STRICT;
#endif /* CONFIG_PROC_SYSCTL */
#endif /* CONFIG_SYSCTL */

/*
 * /proc/sys support
 */

#ifdef CONFIG_PROC_SYSCTL

static int _proc_do_string(char *data, int maxlen, int dir,
                char *buffer, size_t *lenp, loff_t *ppos)
{
        size_t len;
        char c, *p;

        if (!data || !maxlen || !*lenp) {
                *lenp = 0;
                return 0;
        }

        if (SYSCTL_USER_TO_KERN(dir)) {
                if (sysctl_writes_strict == SYSCTL_WRITES_STRICT) {
                        /* Only continue writes not past the end of buffer. */
                        len = strlen(data);
                        if (len > maxlen - 1)
                                len = maxlen - 1;

                        if (*ppos > len)
                                return 0;
                        len = *ppos;
                } else {
                        /* Start writing from beginning of buffer. */
                        len = 0;
                }

                *ppos += *lenp;
                p = buffer;
                while ((p - buffer) < *lenp && len < maxlen - 1) {
                        c = *(p++);
                        if (c == 0 || c == '\n')
                                break;
                        data[len++] = c;
                }
                data[len] = 0;
        } else {
                len = strlen(data);
                if (len > maxlen)
                        len = maxlen;

                if (*ppos > len) {
                        *lenp = 0;
                        return 0;
                }

                data += *ppos;
                len  -= *ppos;

                if (len > *lenp)
                        len = *lenp;
                if (len)
                        memcpy(buffer, data, len);
                if (len < *lenp) {
                        buffer[len] = '\n';
                        len++;
                }
                *lenp = len;
                *ppos += len;
        }
        return 0;
}

static void warn_sysctl_write(const struct ctl_table *table)
{
        pr_warn_once("%s wrote to %s when file position was not 0!\n"
                "This will not be supported in the future. To silence this\n"
                "warning, set kernel.sysctl_writes_strict = -1\n",
                current->comm, table->procname);
}

/**
 * proc_first_pos_non_zero_ignore - check if first position is allowed
 * @ppos: file position
 * @table: the sysctl table
 *
 * Returns true if the first position is non-zero and the sysctl_writes_strict
 * mode indicates this is not allowed for numeric input types. String proc
 * handlers can ignore the return value.
 */
static bool proc_first_pos_non_zero_ignore(loff_t *ppos,
                                           const struct ctl_table *table)
{
        if (!*ppos)
                return false;

        switch (sysctl_writes_strict) {
        case SYSCTL_WRITES_STRICT:
                return true;
        case SYSCTL_WRITES_WARN:
                warn_sysctl_write(table);
                return false;
        default:
                return false;
        }
}

/**
 * proc_dostring - read a string sysctl
 * @table: the sysctl table
 * @dir: %TRUE if this is a write to the sysctl file
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 * @ppos: file position
 *
 * Reads/writes a string from/to the user buffer. If the kernel
 * buffer provided is not large enough to hold the string, the
 * string is truncated. The copied string is %NULL-terminated.
 * If the string is being read by the user process, it is copied
 * and a newline '\n' is added. It is truncated if the buffer is
 * not large enough.
 *
 * Returns 0 on success.
 */
int proc_dostring(const struct ctl_table *table, int dir,
                  void *buffer, size_t *lenp, loff_t *ppos)
{
        if (SYSCTL_USER_TO_KERN(dir))
                proc_first_pos_non_zero_ignore(ppos, table);

        return _proc_do_string(table->data, table->maxlen, dir, buffer, lenp,
                        ppos);
}

static void proc_skip_spaces(char **buf, size_t *size)
{
        while (*size) {
                if (!isspace(**buf))
                        break;
                (*size)--;
                (*buf)++;
        }
}

static void proc_skip_char(char **buf, size_t *size, const char v)
{
        while (*size) {
                if (**buf != v)
                        break;
                (*size)--;
                (*buf)++;
        }
}

/**
 * strtoul_lenient - parse an ASCII formatted integer from a buffer and only
 *                   fail on overflow
 *
 * @cp: kernel buffer containing the string to parse
 * @endp: pointer to store the trailing characters
 * @base: the base to use
 * @res: where the parsed integer will be stored
 *
 * In case of success 0 is returned and @res will contain the parsed integer,
 * @endp will hold any trailing characters.
 * This function will fail the parse on overflow. If there wasn't an overflow
 * the function will defer the decision what characters count as invalid to the
 * caller.
 */
static int strtoul_lenient(const char *cp, char **endp, unsigned int base,
                           unsigned long *res)
{
        unsigned long long result;
        unsigned int rv;

        cp = _parse_integer_fixup_radix(cp, &base);
        rv = _parse_integer(cp, base, &result);
        if ((rv & KSTRTOX_OVERFLOW) || (result != (unsigned long)result))
                return -ERANGE;

        cp += rv;

        if (endp)
                *endp = (char *)cp;

        *res = (unsigned long)result;
        return 0;
}

#define TMPBUFLEN 22
/**
 * proc_get_long - reads an ASCII formatted integer from a user buffer
 *
 * @buf: a kernel buffer
 * @size: size of the kernel buffer
 * @val: this is where the number will be stored
 * @neg: set to %TRUE if number is negative
 * @perm_tr: a vector which contains the allowed trailers
 * @perm_tr_len: size of the perm_tr vector
 * @tr: pointer to store the trailer character
 *
 * In case of success %0 is returned and @buf and @size are updated with
 * the amount of bytes read. If @tr is non-NULL and a trailing
 * character exists (size is non-zero after returning from this
 * function), @tr is updated with the trailing character.
 */
static int proc_get_long(char **buf, size_t *size,
                          unsigned long *val, bool *neg,
                          const char *perm_tr, unsigned perm_tr_len, char *tr)
{
        char *p, tmp[TMPBUFLEN];
        ssize_t len = *size;

        if (len <= 0)
                return -EINVAL;

        if (len > TMPBUFLEN - 1)
                len = TMPBUFLEN - 1;

        memcpy(tmp, *buf, len);

        tmp[len] = 0;
        p = tmp;
        if (*p == '-' && *size > 1) {
                *neg = true;
                p++;
        } else
                *neg = false;
        if (!isdigit(*p))
                return -EINVAL;

        if (strtoul_lenient(p, &p, 0, val))
                return -EINVAL;

        len = p - tmp;

        /* We don't know if the next char is whitespace thus we may accept
         * invalid integers (e.g. 1234...a) or two integers instead of one
         * (e.g. 123...1). So lets not allow such large numbers. */
        if (len == TMPBUFLEN - 1)
                return -EINVAL;

        if (len < *size && perm_tr_len && !memchr(perm_tr, *p, perm_tr_len))
                return -EINVAL;

        if (tr && (len < *size))
                *tr = *p;

        *buf += len;
        *size -= len;

        return 0;
}

/**
 * proc_put_long - converts an integer to a decimal ASCII formatted string
 *
 * @buf: the user buffer
 * @size: the size of the user buffer
 * @val: the integer to be converted
 * @neg: sign of the number, %TRUE for negative
 *
 * In case of success @buf and @size are updated with the amount of bytes
 * written.
 */
static void proc_put_long(void **buf, size_t *size, unsigned long val, bool neg)
{
        int len;
        char tmp[TMPBUFLEN], *p = tmp;

        sprintf(p, "%s%lu", neg ? "-" : "", val);
        len = strlen(tmp);
        if (len > *size)
                len = *size;
        memcpy(*buf, tmp, len);
        *size -= len;
        *buf += len;
}
#undef TMPBUFLEN

static void proc_put_char(void **buf, size_t *size, char c)
{
        if (*size) {
                char **buffer = (char **)buf;
                **buffer = c;

                (*size)--;
                (*buffer)++;
                *buf = *buffer;
        }
}

/**
 * proc_uint_u2k_conv_uop - Assign user value to a kernel pointer
 *
 * @u_ptr: pointer to user space variable
 * @k_ptr: pointer to kernel variable
 * @u_ptr_op: execute this function before assigning to k_ptr
 *
 * Uses WRITE_ONCE to assign value to k_ptr. Executes u_ptr_op if
 * not NULL. Check that the values are less than UINT_MAX to avoid
 * having to support wrap around from userspace.
 *
 * returns 0 on success.
 */
int proc_uint_u2k_conv_uop(const ulong *u_ptr, uint *k_ptr,
                           ulong (*u_ptr_op)(const ulong))
{
        ulong u = u_ptr_op ? u_ptr_op(*u_ptr) : *u_ptr;

        if (u > UINT_MAX)
                return -EINVAL;
        WRITE_ONCE(*k_ptr, u);
        return 0;
}

/**
 * proc_uint_k2u_conv - Assign kernel value to a user space pointer
 *
 * @u_ptr: pointer to user space variable
 * @k_ptr: pointer to kernel variable
 *
 * Uses READ_ONCE to assign value to u_ptr.
 *
 * returns 0 on success.
 */
int proc_uint_k2u_conv(ulong *u_ptr, const uint *k_ptr)
{
        uint val = READ_ONCE(*k_ptr);
        *u_ptr = (ulong)val;
        return 0;
}

/**
 * proc_uint_conv - Change user or kernel pointer based on direction
 *
 * @u_ptr: pointer to user variable
 * @k_ptr: pointer to kernel variable
 * @dir: %TRUE if this is a write to the sysctl file
 * @tbl: the sysctl table
 * @k_ptr_range_check: Check range for k_ptr when %TRUE
 * @user_to_kern: Callback used to assign value from user to kernel var
 * @kern_to_user: Callback used to assign value from kernel to user var
 *
 * When direction is kernel to user, then the u_ptr is modified.
 * When direction is user to kernel, then the k_ptr is modified.
 *
 * Returns 0 on success
 */
int proc_uint_conv(ulong *u_ptr, uint *k_ptr, int dir,
                   const struct ctl_table *tbl, bool k_ptr_range_check,
                   int (*user_to_kern)(const ulong *u_ptr, uint *k_ptr),
                   int (*kern_to_user)(ulong *u_ptr, const uint *k_ptr))
{
        if (SYSCTL_KERN_TO_USER(dir))
                return kern_to_user(u_ptr, k_ptr);

        if (k_ptr_range_check) {
                uint tmp_k;
                int ret;

                if (!tbl)
                        return -EINVAL;
                ret = user_to_kern(u_ptr, &tmp_k);
                if (ret)
                        return ret;
                if ((tbl->extra1 &&
                     *(uint *)tbl->extra1 > tmp_k) ||
                    (tbl->extra2 &&
                     *(uint *)tbl->extra2 < tmp_k))
                        return -ERANGE;
                WRITE_ONCE(*k_ptr, tmp_k);
        } else
                return user_to_kern(u_ptr, k_ptr);
        return 0;
}

static int proc_uint_u2k_conv(const ulong *u_ptr, uint *k_ptr)
{
        return proc_uint_u2k_conv_uop(u_ptr, k_ptr, NULL);
}

static int do_proc_uint_conv(ulong *u_ptr, uint *k_ptr, int dir,
                             const struct ctl_table *tbl)
{
        return proc_uint_conv(u_ptr, k_ptr, dir, tbl, false,
                              proc_uint_u2k_conv, proc_uint_k2u_conv);
}

static int do_proc_uint_conv_minmax(ulong *u_ptr, uint *k_ptr, int dir,
                                    const struct ctl_table *tbl)
{
        return proc_uint_conv(u_ptr, k_ptr, dir, tbl, true,
                              proc_uint_u2k_conv, proc_uint_k2u_conv);
}

/**
 * proc_int_k2u_conv_kop - Assign kernel value to a user space pointer
 * @u_ptr: pointer to user space variable
 * @k_ptr: pointer to kernel variable
 * @negp: assigned %TRUE if the converted kernel value is negative;
 *        %FALSE otherweise
 * @k_ptr_op: execute this function before assigning to u_ptr
 *
 * Uses READ_ONCE to get value from k_ptr. Executes k_ptr_op before assigning
 * to u_ptr if not NULL. Does **not** check for overflow.
 *
 * Returns: 0 on success.
 */
int proc_int_k2u_conv_kop(ulong *u_ptr, const int *k_ptr, bool *negp,
                          ulong (*k_ptr_op)(const ulong))
{
        int val = READ_ONCE(*k_ptr);

        if (val < 0) {
                *negp = true;
                *u_ptr = k_ptr_op ? -k_ptr_op((ulong)val) : -(ulong)val;
        } else {
                *negp = false;
                *u_ptr = k_ptr_op ? k_ptr_op((ulong)val) : (ulong) val;
        }
        return 0;
}

/**
 * proc_int_u2k_conv_uop - Assign user value to a kernel pointer
 * @u_ptr: pointer to user space variable
 * @k_ptr: pointer to kernel variable
 * @negp: If %TRUE, the converted user value is made negative.
 * @u_ptr_op: execute this function before assigning to k_ptr
 *
 * Uses WRITE_ONCE to assign value to k_ptr. Executes u_ptr_op if
 * not NULL. Check for overflow with UINT_MAX.
 *
 * Returns: 0 on success.
 */
int proc_int_u2k_conv_uop(const ulong *u_ptr, int *k_ptr, const bool *negp,
                          ulong (*u_ptr_op)(const ulong))
{
        ulong u = u_ptr_op ? u_ptr_op(*u_ptr) : *u_ptr;

        if (*negp) {
                if (u > (ulong) INT_MAX + 1)
                        return -EINVAL;
                WRITE_ONCE(*k_ptr, -u);
        } else {
                if (u > (ulong) INT_MAX)
                        return -EINVAL;
                WRITE_ONCE(*k_ptr, u);
        }
        return 0;
}

int proc_int_conv(bool *negp, ulong *u_ptr, int *k_ptr, int dir,
                  const struct ctl_table *tbl, bool k_ptr_range_check,
                  int (*user_to_kern)(const bool *negp, const ulong *u_ptr, int *k_ptr),
                  int (*kern_to_user)(bool *negp, ulong *u_ptr, const int *k_ptr))
{
        if (SYSCTL_KERN_TO_USER(dir))
                return kern_to_user(negp, u_ptr, k_ptr);

        if (k_ptr_range_check) {
                int tmp_k, ret;

                if (!tbl)
                        return -EINVAL;
                ret = user_to_kern(negp, u_ptr, &tmp_k);
                if (ret)
                        return ret;
                if ((tbl->extra1 && *(int *)tbl->extra1 > tmp_k) ||
                    (tbl->extra2 && *(int *)tbl->extra2 < tmp_k))
                        return -EINVAL;
                WRITE_ONCE(*k_ptr, tmp_k);
        } else
                return user_to_kern(negp, u_ptr, k_ptr);
        return 0;
}



static int sysctl_user_to_kern_int_conv(const bool *negp, const ulong *u_ptr,
                                        int *k_ptr)
{
        return proc_int_u2k_conv_uop(u_ptr, k_ptr, negp, NULL);
}

static int sysctl_kern_to_user_int_conv(bool *negp, ulong *u_ptr, const int *k_ptr)
{
        return proc_int_k2u_conv_kop(u_ptr, k_ptr, negp, NULL);
}

static int do_proc_int_conv(bool *negp, unsigned long *u_ptr, int *k_ptr,
                            int dir, const struct ctl_table *tbl)
{
        return proc_int_conv(negp, u_ptr, k_ptr, dir, tbl, false,
                             sysctl_user_to_kern_int_conv,
                             sysctl_kern_to_user_int_conv);

}

static int do_proc_int_conv_minmax(bool *negp, unsigned long *u_ptr, int *k_ptr,
                                   int dir, const struct ctl_table *tbl)
{
        return proc_int_conv(negp, u_ptr, k_ptr, dir, tbl, true,
                             sysctl_user_to_kern_int_conv,
                             sysctl_kern_to_user_int_conv);
}

static const char proc_wspace_sep[] = { ' ', '\t', '\n' };

static int do_proc_dointvec(const struct ctl_table *table, int dir,
                  void *buffer, size_t *lenp, loff_t *ppos,
                  int (*conv)(bool *negp, unsigned long *u_ptr, int *k_ptr,
                              int dir, const struct ctl_table *table))
{
        int *i, vleft, first = 1, err = 0;
        size_t left;
        char *p;

        if (!table->data || !table->maxlen || !*lenp ||
            (*ppos && SYSCTL_KERN_TO_USER(dir))) {
                *lenp = 0;
                return 0;
        }

        i = (int *) table->data;
        vleft = table->maxlen / sizeof(*i);
        left = *lenp;

        if (!conv)
                conv = do_proc_int_conv;

        if (SYSCTL_USER_TO_KERN(dir)) {
                if (proc_first_pos_non_zero_ignore(ppos, table))
                        goto out;

                if (left > PAGE_SIZE - 1)
                        left = PAGE_SIZE - 1;
                p = buffer;
        }

        for (; left && vleft--; i++, first=0) {
                unsigned long lval;
                bool neg;

                if (SYSCTL_USER_TO_KERN(dir)) {
                        proc_skip_spaces(&p, &left);

                        if (!left)
                                break;
                        err = proc_get_long(&p, &left, &lval, &neg,
                                             proc_wspace_sep,
                                             sizeof(proc_wspace_sep), NULL);
                        if (err)
                                break;
                        if (conv(&neg, &lval, i, 1, table)) {
                                err = -EINVAL;
                                break;
                        }
                } else {
                        if (conv(&neg, &lval, i, 0, table)) {
                                err = -EINVAL;
                                break;
                        }
                        if (!first)
                                proc_put_char(&buffer, &left, '\t');
                        proc_put_long(&buffer, &left, lval, neg);
                }
        }

        if (SYSCTL_KERN_TO_USER(dir) && !first && left && !err)
                proc_put_char(&buffer, &left, '\n');
        if (SYSCTL_USER_TO_KERN(dir) && !err && left)
                proc_skip_spaces(&p, &left);
        if (SYSCTL_USER_TO_KERN(dir) && first)
                return err ? : -EINVAL;
        *lenp -= left;
out:
        *ppos += *lenp;
        return err;
}

static int do_proc_douintvec_w(const struct ctl_table *table, void *buffer,
                               size_t *lenp, loff_t *ppos,
                               int (*conv)(unsigned long *u_ptr,
                                           unsigned int *k_ptr, int dir,
                                           const struct ctl_table *table))
{
        unsigned long lval;
        int err = 0;
        size_t left;
        bool neg;
        char *p = buffer;

        left = *lenp;

        if (proc_first_pos_non_zero_ignore(ppos, table))
                goto bail_early;

        if (left > PAGE_SIZE - 1)
                left = PAGE_SIZE - 1;

        proc_skip_spaces(&p, &left);
        if (!left) {
                err = -EINVAL;
                goto out_free;
        }

        err = proc_get_long(&p, &left, &lval, &neg,
                             proc_wspace_sep,
                             sizeof(proc_wspace_sep), NULL);
        if (err || neg) {
                err = -EINVAL;
                goto out_free;
        }

        if (conv(&lval, (unsigned int *) table->data, 1, table)) {
                err = -EINVAL;
                goto out_free;
        }

        if (!err && left)
                proc_skip_spaces(&p, &left);

out_free:
        if (err)
                return -EINVAL;

        return 0;

bail_early:
        *ppos += *lenp;
        return err;
}

static int do_proc_douintvec_r(const struct ctl_table *table, void *buffer,
                               size_t *lenp, loff_t *ppos,
                               int (*conv)(unsigned long *u_ptr,
                                           unsigned int *k_ptr, int dir,
                                           const struct ctl_table *table))
{
        unsigned long lval;
        int err = 0;
        size_t left;

        left = *lenp;

        if (conv(&lval, (unsigned int *) table->data, 0, table)) {
                err = -EINVAL;
                goto out;
        }

        proc_put_long(&buffer, &left, lval, false);
        if (!left)
                goto out;

        proc_put_char(&buffer, &left, '\n');

out:
        *lenp -= left;
        *ppos += *lenp;

        return err;
}

static int do_proc_douintvec(const struct ctl_table *table, int dir,
                             void *buffer, size_t *lenp, loff_t *ppos,
                              int (*conv)(unsigned long *u_ptr,
                                          unsigned int *k_ptr, int dir,
                                          const struct ctl_table *table))
{
        unsigned int vleft;

        if (!table->data || !table->maxlen || !*lenp ||
            (*ppos && SYSCTL_KERN_TO_USER(dir))) {
                *lenp = 0;
                return 0;
        }

        vleft = table->maxlen / sizeof(unsigned int);

        /*
         * Arrays are not supported, keep this simple. *Do not* add
         * support for them.
         */
        if (vleft != 1) {
                *lenp = 0;
                return -EINVAL;
        }

        if (!conv)
                conv = do_proc_uint_conv;

        if (SYSCTL_USER_TO_KERN(dir))
                return do_proc_douintvec_w(table, buffer, lenp, ppos, conv);
        return do_proc_douintvec_r(table, buffer, lenp, ppos, conv);
}

/**
 * proc_douintvec_conv - read a vector of unsigned ints with a custom converter
 *
 * @table: the sysctl table
 * @dir: %TRUE if this is a write to the sysctl file
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 * @ppos: file position
 * @conv: Custom converter call back
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned int) unsigned integer
 * values from/to the user buffer, treated as an ASCII string. Negative
 * strings are not allowed.
 *
 * Returns 0 on success
 */
int proc_douintvec_conv(const struct ctl_table *table, int dir, void *buffer,
                        size_t *lenp, loff_t *ppos,
                        int (*conv)(unsigned long *u_ptr, unsigned int *k_ptr,
                                    int dir, const struct ctl_table *table))
{
        return do_proc_douintvec(table, dir, buffer, lenp, ppos, conv);
}

/**
 * proc_dobool - read/write a bool
 * @table: the sysctl table
 * @dir: %TRUE if this is a write to the sysctl file
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 * @ppos: file position
 *
 * Reads/writes one integer value from/to the user buffer,
 * treated as an ASCII string.
 *
 * table->data must point to a bool variable and table->maxlen must
 * be sizeof(bool).
 *
 * Returns 0 on success.
 */
int proc_dobool(const struct ctl_table *table, int dir, void *buffer,
                size_t *lenp, loff_t *ppos)
{
        struct ctl_table tmp;
        bool *data = table->data;
        int res, val;

        /* Do not support arrays yet. */
        if (table->maxlen != sizeof(bool))
                return -EINVAL;

        tmp = *table;
        tmp.maxlen = sizeof(val);
        tmp.data = &val;

        val = READ_ONCE(*data);
        res = proc_dointvec(&tmp, dir, buffer, lenp, ppos);
        if (res)
                return res;
        if (SYSCTL_USER_TO_KERN(dir))
                WRITE_ONCE(*data, val);
        return 0;
}

/**
 * proc_dointvec - read a vector of integers
 * @table: the sysctl table
 * @dir: %TRUE if this is a write to the sysctl file
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 * @ppos: file position
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
 * values from/to the user buffer, treated as an ASCII string.
 *
 * Returns 0 on success.
 */
int proc_dointvec(const struct ctl_table *table, int dir, void *buffer,
                  size_t *lenp, loff_t *ppos)
{
        return do_proc_dointvec(table, dir, buffer, lenp, ppos, NULL);
}

/**
 * proc_douintvec - read a vector of unsigned integers
 * @table: the sysctl table
 * @dir: %TRUE if this is a write to the sysctl file
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 * @ppos: file position
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned int) unsigned integer
 * values from/to the user buffer, treated as an ASCII string.
 *
 * Returns 0 on success.
 */
int proc_douintvec(const struct ctl_table *table, int dir, void *buffer,
                size_t *lenp, loff_t *ppos)
{
        return do_proc_douintvec(table, dir, buffer, lenp, ppos,
                                 do_proc_uint_conv);
}

/**
 * proc_dointvec_minmax - read a vector of integers with min/max values
 * @table: the sysctl table
 * @dir: %TRUE if this is a write to the sysctl file
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 * @ppos: file position
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
 * values from/to the user buffer, treated as an ASCII string.
 *
 * This routine will ensure the values are within the range specified by
 * table->extra1 (min) and table->extra2 (max).
 *
 * Returns 0 on success or -EINVAL when the range check fails and
 * SYSCTL_USER_TO_KERN(dir) == true
 */
int proc_dointvec_minmax(const struct ctl_table *table, int dir,
                  void *buffer, size_t *lenp, loff_t *ppos)
{
        return do_proc_dointvec(table, dir, buffer, lenp, ppos,
                                do_proc_int_conv_minmax);
}

/**
 * proc_douintvec_minmax - read a vector of unsigned ints with min/max values
 * @table: the sysctl table
 * @dir: %TRUE if this is a write to the sysctl file
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 * @ppos: file position
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned int) unsigned integer
 * values from/to the user buffer, treated as an ASCII string. Negative
 * strings are not allowed.
 *
 * When changing the kernel variable, this routine will ensure the values
 * are within the range specified by table->extra1 (min) and table->extra2
 * (max). And Check that the values are less than UINT_MAX to avoid having to
 * support wrap around uses from userspace.
 *
 * Returns 0 on success or -ERANGE when range check failes and
 * SYSCTL_USER_TO_KERN(dir) == true
 */
int proc_douintvec_minmax(const struct ctl_table *table, int dir,
                          void *buffer, size_t *lenp, loff_t *ppos)
{
        return do_proc_douintvec(table, dir, buffer, lenp, ppos,
                                 do_proc_uint_conv_minmax);
}

/**
 * proc_dou8vec_minmax - read a vector of unsigned chars with min/max values
 * @table: the sysctl table
 * @dir: %TRUE if this is a write to the sysctl file
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 * @ppos: file position
 *
 * Reads/writes up to table->maxlen/sizeof(u8) unsigned chars
 * values from/to the user buffer, treated as an ASCII string. Negative
 * strings are not allowed.
 *
 * This routine will ensure the values are within the range specified by
 * table->extra1 (min) and table->extra2 (max).
 *
 * Returns 0 on success or an error on SYSCTL_USER_TO_KERN(dir) == true
 * and the range check fails.
 */
int proc_dou8vec_minmax(const struct ctl_table *table, int dir,
                        void *buffer, size_t *lenp, loff_t *ppos)
{
        struct ctl_table tmp;
        unsigned int min = 0, max = 255U, val;
        u8 *data = table->data;
        int res;

        /* Do not support arrays yet. */
        if (table->maxlen != sizeof(u8))
                return -EINVAL;

        tmp = *table;

        tmp.maxlen = sizeof(val);
        tmp.data = &val;
        if (!tmp.extra1)
                tmp.extra1 = (unsigned int *) &min;
        if (!tmp.extra2)
                tmp.extra2 = (unsigned int *) &max;

        val = READ_ONCE(*data);
        res = do_proc_douintvec(&tmp, dir, buffer, lenp, ppos,
                                do_proc_uint_conv_minmax);
        if (res)
                return res;
        if (SYSCTL_USER_TO_KERN(dir))
                WRITE_ONCE(*data, val);
        return 0;
}
EXPORT_SYMBOL_GPL(proc_dou8vec_minmax);

static int do_proc_doulongvec_minmax(const struct ctl_table *table, int dir,
                                     void *buffer, size_t *lenp, loff_t *ppos,
                                     unsigned long convmul,
                                     unsigned long convdiv)
{
        unsigned long *i, *min, *max;
        int vleft, first = 1, err = 0;
        size_t left;
        char *p;

        if (!table->data || !table->maxlen || !*lenp ||
            (*ppos && SYSCTL_KERN_TO_USER(dir))) {
                *lenp = 0;
                return 0;
        }

        i = table->data;
        min = table->extra1;
        max = table->extra2;
        vleft = table->maxlen / sizeof(unsigned long);
        left = *lenp;

        if (SYSCTL_USER_TO_KERN(dir)) {
                if (proc_first_pos_non_zero_ignore(ppos, table))
                        goto out;

                if (left > PAGE_SIZE - 1)
                        left = PAGE_SIZE - 1;
                p = buffer;
        }

        for (; left && vleft--; i++, first = 0) {
                unsigned long val;

                if (SYSCTL_USER_TO_KERN(dir)) {
                        bool neg;

                        proc_skip_spaces(&p, &left);
                        if (!left)
                                break;

                        err = proc_get_long(&p, &left, &val, &neg,
                                             proc_wspace_sep,
                                             sizeof(proc_wspace_sep), NULL);
                        if (err || neg) {
                                err = -EINVAL;
                                break;
                        }

                        val = convmul * val / convdiv;
                        if ((min && val < *min) || (max && val > *max)) {
                                err = -EINVAL;
                                break;
                        }
                        WRITE_ONCE(*i, val);
                } else {
                        val = convdiv * READ_ONCE(*i) / convmul;
                        if (!first)
                                proc_put_char(&buffer, &left, '\t');
                        proc_put_long(&buffer, &left, val, false);
                }
        }

        if (SYSCTL_KERN_TO_USER(dir) && !first && left && !err)
                proc_put_char(&buffer, &left, '\n');
        if (SYSCTL_USER_TO_KERN(dir) && !err)
                proc_skip_spaces(&p, &left);
        if (SYSCTL_USER_TO_KERN(dir) && first)
                return err ? : -EINVAL;
        *lenp -= left;
out:
        *ppos += *lenp;
        return err;
}

int proc_doulongvec_minmax_conv(const struct ctl_table *table, int dir,
                                void *buffer, size_t *lenp, loff_t *ppos,
                                unsigned long convmul, unsigned long convdiv)
{
        return do_proc_doulongvec_minmax(table, dir, buffer, lenp, ppos,
                                         convmul, convdiv);
}

/**
 * proc_doulongvec_minmax - read a vector of long integers with min/max values
 * @table: the sysctl table
 * @dir: %TRUE if this is a write to the sysctl file
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 * @ppos: file position
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned long) unsigned long
 * values from/to the user buffer, treated as an ASCII string.
 *
 * This routine will ensure the values are within the range specified by
 * table->extra1 (min) and table->extra2 (max).
 *
 * Returns 0 on success.
 */
int proc_doulongvec_minmax(const struct ctl_table *table, int dir,
                           void *buffer, size_t *lenp, loff_t *ppos)
{
        return proc_doulongvec_minmax_conv(table, dir, buffer, lenp, ppos, 1l, 1l);
}

/**
 * proc_dointvec_conv - read a vector of ints with a custom converter
 * @table: the sysctl table
 * @dir: %TRUE if this is a write to the sysctl file
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 * @ppos: file position
 * @conv: Custom converter call back
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned int) unsigned integer
 * values from/to the user buffer, treated as an ASCII string. Negative
 * strings are not allowed.
 *
 * Returns: 0 on success
 */

int proc_dointvec_conv(const struct ctl_table *table, int dir, void *buffer,
                       size_t *lenp, loff_t *ppos,
                       int (*conv)(bool *negp, unsigned long *u_ptr, int *k_ptr,
                                   int dir, const struct ctl_table *table))
{
        return do_proc_dointvec(table, dir, buffer, lenp, ppos, conv);
}

/**
 * proc_do_large_bitmap - read/write from/to a large bitmap
 * @table: the sysctl table
 * @dir: %TRUE if this is a write to the sysctl file
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 * @ppos: file position
 *
 * The bitmap is stored at table->data and the bitmap length (in bits)
 * in table->maxlen.
 *
 * We use a range comma separated format (e.g. 1,3-4,10-10) so that
 * large bitmaps may be represented in a compact manner. Writing into
 * the file will clear the bitmap then update it with the given input.
 *
 * Returns 0 on success.
 */
int proc_do_large_bitmap(const struct ctl_table *table, int dir,
                         void *buffer, size_t *lenp, loff_t *ppos)
{
        int err = 0;
        size_t left = *lenp;
        unsigned long bitmap_len = table->maxlen;
        unsigned long *bitmap = *(unsigned long **) table->data;
        unsigned long *tmp_bitmap = NULL;
        char tr_a[] = { '-', ',', '\n' }, tr_b[] = { ',', '\n', 0 }, c = 0;

        if (!bitmap || !bitmap_len || !left || (*ppos && SYSCTL_KERN_TO_USER(dir))) {
                *lenp = 0;
                return 0;
        }

        if (SYSCTL_USER_TO_KERN(dir)) {
                char *p = buffer;
                size_t skipped = 0;

                if (left > PAGE_SIZE - 1) {
                        left = PAGE_SIZE - 1;
                        /* How much of the buffer we'll skip this pass */
                        skipped = *lenp - left;
                }

                tmp_bitmap = bitmap_zalloc(bitmap_len, GFP_KERNEL);
                if (!tmp_bitmap)
                        return -ENOMEM;
                proc_skip_char(&p, &left, '\n');
                while (!err && left) {
                        unsigned long val_a, val_b;
                        bool neg;
                        size_t saved_left;

                        /* In case we stop parsing mid-number, we can reset */
                        saved_left = left;
                        err = proc_get_long(&p, &left, &val_a, &neg, tr_a,
                                             sizeof(tr_a), &c);
                        /*
                         * If we consumed the entirety of a truncated buffer or
                         * only one char is left (may be a "-"), then stop here,
                         * reset, & come back for more.
                         */
                        if ((left <= 1) && skipped) {
                                left = saved_left;
                                break;
                        }

                        if (err)
                                break;
                        if (val_a >= bitmap_len || neg) {
                                err = -EINVAL;
                                break;
                        }

                        val_b = val_a;
                        if (left) {
                                p++;
                                left--;
                        }

                        if (c == '-') {
                                err = proc_get_long(&p, &left, &val_b,
                                                     &neg, tr_b, sizeof(tr_b),
                                                     &c);
                                /*
                                 * If we consumed all of a truncated buffer or
                                 * then stop here, reset, & come back for more.
                                 */
                                if (!left && skipped) {
                                        left = saved_left;
                                        break;
                                }

                                if (err)
                                        break;
                                if (val_b >= bitmap_len || neg ||
                                    val_a > val_b) {
                                        err = -EINVAL;
                                        break;
                                }
                                if (left) {
                                        p++;
                                        left--;
                                }
                        }

                        bitmap_set(tmp_bitmap, val_a, val_b - val_a + 1);
                        proc_skip_char(&p, &left, '\n');
                }
                left += skipped;
        } else {
                unsigned long bit_a, bit_b = 0;
                bool first = 1;

                while (left) {
                        bit_a = find_next_bit(bitmap, bitmap_len, bit_b);
                        if (bit_a >= bitmap_len)
                                break;
                        bit_b = find_next_zero_bit(bitmap, bitmap_len,
                                                   bit_a + 1) - 1;

                        if (!first)
                                proc_put_char(&buffer, &left, ',');
                        proc_put_long(&buffer, &left, bit_a, false);
                        if (bit_a != bit_b) {
                                proc_put_char(&buffer, &left, '-');
                                proc_put_long(&buffer, &left, bit_b, false);
                        }

                        first = 0; bit_b++;
                }
                proc_put_char(&buffer, &left, '\n');
        }

        if (!err) {
                if (SYSCTL_USER_TO_KERN(dir)) {
                        if (*ppos)
                                bitmap_or(bitmap, bitmap, tmp_bitmap, bitmap_len);
                        else
                                bitmap_copy(bitmap, tmp_bitmap, bitmap_len);
                }
                *lenp -= left;
                *ppos += *lenp;
        }

        bitmap_free(tmp_bitmap);
        return err;
}

#else /* CONFIG_PROC_SYSCTL */

int proc_dostring(const struct ctl_table *table, int dir,
                  void *buffer, size_t *lenp, loff_t *ppos)
{
        return -ENOSYS;
}

int proc_dobool(const struct ctl_table *table, int dir,
                void *buffer, size_t *lenp, loff_t *ppos)
{
        return -ENOSYS;
}

int proc_dointvec(const struct ctl_table *table, int dir,
                  void *buffer, size_t *lenp, loff_t *ppos)
{
        return -ENOSYS;
}

int proc_douintvec(const struct ctl_table *table, int dir,
                  void *buffer, size_t *lenp, loff_t *ppos)
{
        return -ENOSYS;
}

int proc_dointvec_minmax(const struct ctl_table *table, int dir,
                    void *buffer, size_t *lenp, loff_t *ppos)
{
        return -ENOSYS;
}

int proc_douintvec_minmax(const struct ctl_table *table, int dir,
                          void *buffer, size_t *lenp, loff_t *ppos)
{
        return -ENOSYS;
}

int proc_douintvec_conv(const struct ctl_table *table, int write, void *buffer,
                        size_t *lenp, loff_t *ppos,
                        int (*conv)(unsigned long *lvalp, unsigned int *valp,
                                    int write, const struct ctl_table *table))
{
        return -ENOSYS;
}

int proc_uint_k2u_conv(ulong *u_ptr, const uint *k_ptr)
{
        return -ENOSYS;
}

int proc_uint_u2k_conv_uop(const ulong *u_ptr, uint *k_ptr,
                           ulong (*u_ptr_op)(const ulong))
{
        return -ENOSYS;
}

int proc_uint_conv(ulong *u_ptr, uint *k_ptr, int dir,
                   const struct ctl_table *tbl, bool k_ptr_range_check,
                   int (*user_to_kern)(const ulong *u_ptr, uint *k_ptr),
                   int (*kern_to_user)(ulong *u_ptr, const uint *k_ptr))
{
        return -ENOSYS;
}

int proc_dou8vec_minmax(const struct ctl_table *table, int dir,
                        void *buffer, size_t *lenp, loff_t *ppos)
{
        return -ENOSYS;
}

int proc_doulongvec_minmax(const struct ctl_table *table, int dir,
                    void *buffer, size_t *lenp, loff_t *ppos)
{
        return -ENOSYS;
}

int proc_doulongvec_minmax_conv(const struct ctl_table *table, int dir,
                                void *buffer, size_t *lenp, loff_t *ppos,
                                unsigned long convmul, unsigned long convdiv)
{
        return -ENOSYS;
}

int proc_dointvec_conv(const struct ctl_table *table, int dir, void *buffer,
                       size_t *lenp, loff_t *ppos,
                       int (*conv)(bool *negp, unsigned long *u_ptr, int *k_ptr,
                                   int dir, const struct ctl_table *table))
{
        return -ENOSYS;
}

int proc_do_large_bitmap(const struct ctl_table *table, int dir,
                         void *buffer, size_t *lenp, loff_t *ppos)
{
        return -ENOSYS;
}

#endif /* CONFIG_PROC_SYSCTL */

#if defined(CONFIG_SYSCTL)
int proc_do_static_key(const struct ctl_table *table, int dir,
                       void *buffer, size_t *lenp, loff_t *ppos)
{
        struct static_key *key = (struct static_key *)table->data;
        static DEFINE_MUTEX(static_key_mutex);
        int val, ret;
        struct ctl_table tmp = {
                .data   = &val,
                .maxlen = sizeof(val),
                .mode   = table->mode,
                .extra1 = SYSCTL_ZERO,
                .extra2 = SYSCTL_ONE,
        };

        if (SYSCTL_USER_TO_KERN(dir) && !capable(CAP_SYS_ADMIN))
                return -EPERM;

        mutex_lock(&static_key_mutex);
        val = static_key_enabled(key);
        ret = proc_dointvec_minmax(&tmp, dir, buffer, lenp, ppos);
        if (SYSCTL_USER_TO_KERN(dir) && !ret) {
                if (val)
                        static_key_enable(key);
                else
                        static_key_disable(key);
        }
        mutex_unlock(&static_key_mutex);
        return ret;
}

static const struct ctl_table sysctl_subsys_table[] = {
#ifdef CONFIG_PROC_SYSCTL
        {
                .procname       = "sysctl_writes_strict",
                .data           = &sysctl_writes_strict,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = SYSCTL_NEG_ONE,
                .extra2         = SYSCTL_ONE,
        },
#endif
        {
                .procname       = "ngroups_max",
                .data           = (void *)&ngroups_max,
                .maxlen         = sizeof (int),
                .mode           = 0444,
                .proc_handler   = proc_dointvec,
        },
        {
                .procname       = "cap_last_cap",
                .data           = (void *)&cap_last_cap,
                .maxlen         = sizeof(int),
                .mode           = 0444,
                .proc_handler   = proc_dointvec,
        },
#ifdef CONFIG_SYSCTL_ARCH_UNALIGN_ALLOW
        {
                .procname       = "unaligned-trap",
                .data           = &unaligned_enabled,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
#endif
#ifdef CONFIG_SYSCTL_ARCH_UNALIGN_NO_WARN
        {
                .procname       = "ignore-unaligned-usertrap",
                .data           = &no_unaligned_warning,
                .maxlen         = sizeof (int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
#endif
};

int __init sysctl_init_bases(void)
{
        register_sysctl_init("kernel", sysctl_subsys_table);

        return 0;
}
#endif /* CONFIG_SYSCTL */
/*
 * No sense putting this after each symbol definition, twice,
 * exception granted :-)
 */
EXPORT_SYMBOL(proc_dobool);
EXPORT_SYMBOL(proc_dointvec);
EXPORT_SYMBOL(proc_douintvec);
EXPORT_SYMBOL(proc_dointvec_minmax);
EXPORT_SYMBOL_GPL(proc_douintvec_minmax);
EXPORT_SYMBOL(proc_dostring);
EXPORT_SYMBOL(proc_doulongvec_minmax);
EXPORT_SYMBOL(proc_do_large_bitmap);