utimes.c

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#include <linux/compiler.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/linkage.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/sched.h>
#include <linux/stat.h>
#include <linux/utime.h>
#include <linux/syscalls.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>

#ifdef __ARCH_WANT_SYS_UTIME

/*
 * sys_utime() can be implemented in user-level using sys_utimes().
 * Is this for backwards compatibility?  If so, why not move it
 * into the appropriate arch directory (for those architectures that
 * need it).
 */

/* If times==NULL, set access and modification to current time,
 * must be owner or have write permission.
 * Else, update from *times, must be owner or super user.
 */
SYSCALL_DEFINE2(utime, char __user *, filename, struct utimbuf __user *, times)
{
    struct timespec tv[2];

    if (times) {
        if (get_user(tv[0].tv_sec, &times->actime) ||
            get_user(tv[1].tv_sec, &times->modtime))
            return -EFAULT;
        tv[0].tv_nsec = 0;
        tv[1].tv_nsec = 0;
    }
    return do_utimes(AT_FDCWD, filename, times ? tv : NULL, 0);
}

#endif

static bool nsec_valid(long nsec)
{
    if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
        return true;

    return nsec >= 0 && nsec <= 999999999;
}

static int utimes_common(struct path *path, struct timespec *times)
{
    int error;
    struct iattr newattrs;
    struct inode *inode = path->dentry->d_inode;

    error = mnt_want_write(path->mnt);
    if (error)
        goto out;

    if (times && times[0].tv_nsec == UTIME_NOW &&
             times[1].tv_nsec == UTIME_NOW)
        times = NULL;

    newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
    if (times) {
        if (times[0].tv_nsec == UTIME_OMIT)
            newattrs.ia_valid &= ~ATTR_ATIME;
        else if (times[0].tv_nsec != UTIME_NOW) {
            newattrs.ia_atime.tv_sec = times[0].tv_sec;
            newattrs.ia_atime.tv_nsec = times[0].tv_nsec;
            newattrs.ia_valid |= ATTR_ATIME_SET;
        }

        if (times[1].tv_nsec == UTIME_OMIT)
            newattrs.ia_valid &= ~ATTR_MTIME;
        else if (times[1].tv_nsec != UTIME_NOW) {
            newattrs.ia_mtime.tv_sec = times[1].tv_sec;
            newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
            newattrs.ia_valid |= ATTR_MTIME_SET;
        }
        /*
         * Tell inode_change_ok(), that this is an explicit time
         * update, even if neither ATTR_ATIME_SET nor ATTR_MTIME_SET
         * were used.
         */
        newattrs.ia_valid |= ATTR_TIMES_SET;
    } else {
        /*
         * If times is NULL (or both times are UTIME_NOW),
         * then we need to check permissions, because
         * inode_change_ok() won't do it.
         */
        error = -EACCES;
                if (IS_IMMUTABLE(inode))
            goto mnt_drop_write_and_out;

        if (!inode_owner_or_capable(inode)) {
            error = inode_permission(inode, MAY_WRITE);
            if (error)
                goto mnt_drop_write_and_out;
        }
    }
    mutex_lock(&inode->i_mutex);
    error = notify_change(path->dentry, &newattrs);
    mutex_unlock(&inode->i_mutex);

mnt_drop_write_and_out:
    mnt_drop_write(path->mnt);
out:
    return error;
}

/*
 * do_utimes - change times on filename or file descriptor
 * @dfd: open file descriptor, -1 or AT_FDCWD
 * @filename: path name or NULL
 * @times: new times or NULL
 * @flags: zero or more flags (only AT_SYMLINK_NOFOLLOW for the moment)
 *
 * If filename is NULL and dfd refers to an open file, then operate on
 * the file.  Otherwise look up filename, possibly using dfd as a
 * starting point.
 *
 * If times==NULL, set access and modification to current time,
 * must be owner or have write permission.
 * Else, update from *times, must be owner or super user.
 */
long do_utimes(int dfd, const char __user *filename, struct timespec *times,
           int flags)
{
    int error = -EINVAL;

    if (times && (!nsec_valid(times[0].tv_nsec) ||
              !nsec_valid(times[1].tv_nsec))) {
        goto out;
    }

    if (flags & ~AT_SYMLINK_NOFOLLOW)
        goto out;

    if (filename == NULL && dfd != AT_FDCWD) {
        struct fd f;

        if (flags & AT_SYMLINK_NOFOLLOW)
            goto out;

        f = fdget(dfd);
        error = -EBADF;
        if (!f.file)
            goto out;

        error = utimes_common(&f.file->f_path, times);
        fdput(f);
    } else {
        struct path path;
        int lookup_flags = 0;

        if (!(flags & AT_SYMLINK_NOFOLLOW))
            lookup_flags |= LOOKUP_FOLLOW;

        error = user_path_at(dfd, filename, lookup_flags, &path);
        if (error)
            goto out;

        error = utimes_common(&path, times);
        path_put(&path);
    }

out:
    return error;
}

SYSCALL_DEFINE4(utimensat, int, dfd, const char __user *, filename,
        struct timespec __user *, utimes, int, flags)
{
    struct timespec tstimes[2];

    if (utimes) {
        if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
            return -EFAULT;

        /* Nothing to do, we must not even check the path.  */
        if (tstimes[0].tv_nsec == UTIME_OMIT &&
            tstimes[1].tv_nsec == UTIME_OMIT)
            return 0;
    }

    return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
}

SYSCALL_DEFINE3(futimesat, int, dfd, const char __user *, filename,
        struct timeval __user *, utimes)
{
    struct timeval times[2];
    struct timespec tstimes[2];

    if (utimes) {
        if (copy_from_user(&times, utimes, sizeof(times)))
            return -EFAULT;

        /* This test is needed to catch all invalid values.  If we
           would test only in do_utimes we would miss those invalid
           values truncated by the multiplication with 1000.  Note
           that we also catch UTIME_{NOW,OMIT} here which are only
           valid for utimensat.  */
        if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
            times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
            return -EINVAL;

        tstimes[0].tv_sec = times[0].tv_sec;
        tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
        tstimes[1].tv_sec = times[1].tv_sec;
        tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
    }

    return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
}

SYSCALL_DEFINE2(utimes, char __user *, filename,
        struct timeval __user *, utimes)
{
    return sys_futimesat(AT_FDCWD, filename, utimes);
}