fs/utimes.c

   1 #include <linux/compiler.h>
   2 #include <linux/file.h>
   3 #include <linux/fs.h>
   4 #include <linux/linkage.h>
   5 #include <linux/mount.h>
   6 #include <linux/namei.h>
   7 #include <linux/sched.h>
   8 #include <linux/stat.h>
   9 #include <linux/utime.h>
  10 #include <linux/syscalls.h>
  11 #include <asm/uaccess.h>
  12 #include <asm/unistd.h>
  13
  14 #ifdef __ARCH_WANT_SYS_UTIME
  15
  16 /*
  17  * sys_utime() can be implemented in user-level using sys_utimes().
  18  * Is this for backwards compatibility?  If so, why not move it
  19  * into the appropriate arch directory (for those architectures that
  20  * need it).
  21  */
  22
  23 /* If times==NULL, set access and modification to current time,
  24  * must be owner or have write permission.
  25  * Else, update from *times, must be owner or super user.
  26  */
  27 SYSCALL_DEFINE2(utime, char __user *, filename, struct utimbuf __user *, times)
  28 {
  29         struct timespec tv[2];
  30
  31         if (times) {
  32                 if (get_user(tv[0].tv_sec, &times->actime) ||
  33                     get_user(tv[1].tv_sec, &times->modtime))
  34                         return -EFAULT;
  35                 tv[0].tv_nsec = 0;
  36                 tv[1].tv_nsec = 0;
  37         }
  38         return do_utimes(AT_FDCWD, filename, times ? tv : NULL, 0);
  39 }
  40
  41 #endif
  42
  43 static bool nsec_valid(long nsec)
  44 {
  45         if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
  46                 return true;
  47
  48         return nsec >= 0 && nsec <= 999999999;
  49 }
  50
  51 static int utimes_common(struct path *path, struct timespec *times)
  52 {
  53         int error;
  54         struct iattr newattrs;
  55         struct inode *inode = path->dentry->d_inode;
  56
  57         error = mnt_want_write(path->mnt);
  58         if (error)
  59                 goto out;
  60
  61         if (times && times[0].tv_nsec == UTIME_NOW &&
  62                      times[1].tv_nsec == UTIME_NOW)
  63                 times = NULL;
  64
  65         newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
  66         if (times) {
  67                 if (times[0].tv_nsec == UTIME_OMIT)
  68                         newattrs.ia_valid &= ~ATTR_ATIME;
  69                 else if (times[0].tv_nsec != UTIME_NOW) {
  70                         newattrs.ia_atime.tv_sec = times[0].tv_sec;
  71                         newattrs.ia_atime.tv_nsec = times[0].tv_nsec;
  72                         newattrs.ia_valid |= ATTR_ATIME_SET;
  73                 }
  74
  75                 if (times[1].tv_nsec == UTIME_OMIT)
  76                         newattrs.ia_valid &= ~ATTR_MTIME;
  77                 else if (times[1].tv_nsec != UTIME_NOW) {
  78                         newattrs.ia_mtime.tv_sec = times[1].tv_sec;
  79                         newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
  80                         newattrs.ia_valid |= ATTR_MTIME_SET;
  81                 }
  82                 /*
  83                  * Tell inode_change_ok(), that this is an explicit time
  84                  * update, even if neither ATTR_ATIME_SET nor ATTR_MTIME_SET
  85                  * were used.
  86                  */
  87                 newattrs.ia_valid |= ATTR_TIMES_SET;
  88         } else {
  89                 /*
  90                  * If times is NULL (or both times are UTIME_NOW),
  91                  * then we need to check permissions, because
  92                  * inode_change_ok() won't do it.
  93                  */
  94                 error = -EACCES;
  95                 if (IS_IMMUTABLE(inode))
  96                         goto mnt_drop_write_and_out;
  97
  98                 if (!inode_owner_or_capable(inode)) {
  99                         error = inode_permission(inode, MAY_WRITE);
 100                         if (error)
 101                                 goto mnt_drop_write_and_out;
 102                 }
 103         }
 104         mutex_lock(&inode->i_mutex);
 105         error = notify_change(path->dentry, &newattrs);
 106         mutex_unlock(&inode->i_mutex);
 107
 108 mnt_drop_write_and_out:
 109         mnt_drop_write(path->mnt);
 110 out:
 111         return error;
 112 }
 113
 114 /*
 115  * do_utimes - change times on filename or file descriptor
 116  * @dfd: open file descriptor, -1 or AT_FDCWD
 117  * @filename: path name or NULL
 118  * @times: new times or NULL
 119  * @flags: zero or more flags (only AT_SYMLINK_NOFOLLOW for the moment)
 120  *
 121  * If filename is NULL and dfd refers to an open file, then operate on
 122  * the file.  Otherwise look up filename, possibly using dfd as a
 123  * starting point.
 124  *
 125  * If times==NULL, set access and modification to current time,
 126  * must be owner or have write permission.
 127  * Else, update from *times, must be owner or super user.
 128  */
 129 long do_utimes(int dfd, const char __user *filename, struct timespec *times,
 130                int flags)
 131 {
 132         int error = -EINVAL;
 133
 134         if (times && (!nsec_valid(times[0].tv_nsec) ||
 135                       !nsec_valid(times[1].tv_nsec))) {
 136                 goto out;
 137         }
 138
 139         if (flags & ~AT_SYMLINK_NOFOLLOW)
 140                 goto out;
 141
 142         if (filename == NULL && dfd != AT_FDCWD) {
 143                 struct fd f;
 144
 145                 if (flags & AT_SYMLINK_NOFOLLOW)
 146                         goto out;
 147
 148                 f = fdget(dfd);
 149                 error = -EBADF;
 150                 if (!f.file)
 151                         goto out;
 152
 153                 error = utimes_common(&f.file->f_path, times);
 154                 fdput(f);
 155         } else {
 156                 struct path path;
 157                 int lookup_flags = 0;
 158
 159                 if (!(flags & AT_SYMLINK_NOFOLLOW))
 160                         lookup_flags |= LOOKUP_FOLLOW;
 161 retry:
 162                 error = user_path_at(dfd, filename, lookup_flags, &path);
 163                 if (error)
 164                         goto out;
 165
 166                 error = utimes_common(&path, times);
 167                 path_put(&path);
 168                 if (retry_estale(error, lookup_flags)) {
 169                         lookup_flags |= LOOKUP_REVAL;
 170                         goto retry;
 171                 }
 172         }
 173
 174 out:
 175         return error;
 176 }
 177
 178 SYSCALL_DEFINE4(utimensat, int, dfd, const char __user *, filename,
 179                 struct timespec __user *, utimes, int, flags)
 180 {
 181         struct timespec tstimes[2];
 182
 183         if (utimes) {
 184                 if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
 185                         return -EFAULT;
 186
 187                 /* Nothing to do, we must not even check the path.  */
 188                 if (tstimes[0].tv_nsec == UTIME_OMIT &&
 189                     tstimes[1].tv_nsec == UTIME_OMIT)
 190                         return 0;
 191         }
 192
 193         return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
 194 }
 195
 196 SYSCALL_DEFINE3(futimesat, int, dfd, const char __user *, filename,
 197                 struct timeval __user *, utimes)
 198 {
 199         struct timeval times[2];
 200         struct timespec tstimes[2];
 201
 202         if (utimes) {
 203                 if (copy_from_user(&times, utimes, sizeof(times)))
 204                         return -EFAULT;
 205
 206                 /* This test is needed to catch all invalid values.  If we
 207                    would test only in do_utimes we would miss those invalid
 208                    values truncated by the multiplication with 1000.  Note
 209                    that we also catch UTIME_{NOW,OMIT} here which are only
 210                    valid for utimensat.  */
 211                 if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
 212                     times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
 213                         return -EINVAL;
 214
 215                 tstimes[0].tv_sec = times[0].tv_sec;
 216                 tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
 217                 tstimes[1].tv_sec = times[1].tv_sec;
 218                 tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
 219         }
 220
 221         return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
 222 }
 223
 224 SYSCALL_DEFINE2(utimes, char __user *, filename,
 225                 struct timeval __user *, utimes)
 226 {
 227         return sys_futimesat(AT_FDCWD, filename, utimes);
 228 }