root/fs/utimes.c

DEFINITIONS

1. sys_utime
2. nsec_valid
3. utimes_common
4. do_utimes
5. sys_utimensat
6. sys_futimesat
7. sys_utimes

#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.
 */
asmlinkage long sys_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 (!is_owner_or_cap(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, 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 file *file;

                if (flags & AT_SYMLINK_NOFOLLOW)
                        goto out;

                file = fget(dfd);
                error = -EBADF;
                if (!file)
                        goto out;

                error = utimes_common(&file->f_path, times);
                fput(file);
        } 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;
}

asmlinkage long sys_utimensat(int dfd, 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);
}

asmlinkage long sys_futimesat(int dfd, 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);
}

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