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         struct inode *delegated_inode = NULL;
  57
  58         error = mnt_want_write(path->mnt);
  59         if (error)
  60                 goto out;
  61
  62         if (times && times[0].tv_nsec == UTIME_NOW &&
  63                      times[1].tv_nsec == UTIME_NOW)
  64                 times = NULL;
  65
  66         newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
  67         if (times) {
  68                 if (times[0].tv_nsec == UTIME_OMIT)
  69                         newattrs.ia_valid &= ~ATTR_ATIME;
  70                 else if (times[0].tv_nsec != UTIME_NOW) {
  71                         newattrs.ia_atime.tv_sec = times[0].tv_sec;
  72                         newattrs.ia_atime.tv_nsec = times[0].tv_nsec;
  73                         newattrs.ia_valid |= ATTR_ATIME_SET;
  74                 }
  75
  76                 if (times[1].tv_nsec == UTIME_OMIT)
  77                         newattrs.ia_valid &= ~ATTR_MTIME;
  78                 else if (times[1].tv_nsec != UTIME_NOW) {
  79                         newattrs.ia_mtime.tv_sec = times[1].tv_sec;
  80                         newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
  81                         newattrs.ia_valid |= ATTR_MTIME_SET;
  82                 }
  83                 /*
  84                  * Tell inode_change_ok(), that this is an explicit time
  85                  * update, even if neither ATTR_ATIME_SET nor ATTR_MTIME_SET
  86                  * were used.
  87                  */
  88                 newattrs.ia_valid |= ATTR_TIMES_SET;
  89         } else {
  90                 /*
  91                  * If times is NULL (or both times are UTIME_NOW),
  92                  * then we need to check permissions, because
  93                  * inode_change_ok() won't do it.
  94                  */
  95                 error = -EPERM;
  96                 if (IS_IMMUTABLE(inode))
  97                         goto mnt_drop_write_and_out;
  98
  99                 error = -EACCES;
 100                 if (!inode_owner_or_capable(inode)) {
 101                         error = inode_permission(inode, MAY_WRITE);
 102                         if (error)
 103                                 goto mnt_drop_write_and_out;
 104                 }
 105         }
 106 retry_deleg:
 107         inode_lock(inode);
 108         error = notify_change(path->dentry, &newattrs, &delegated_inode);
 109         inode_unlock(inode);
 110         if (delegated_inode) {
 111                 error = break_deleg_wait(&delegated_inode);
 112                 if (!error)
 113                         goto retry_deleg;
 114         }
 115
 116 mnt_drop_write_and_out:
 117         mnt_drop_write(path->mnt);
 118 out:
 119         return error;
 120 }
 121
 122 /*
 123  * do_utimes - change times on filename or file descriptor
 124  * @dfd: open file descriptor, -1 or AT_FDCWD
 125  * @filename: path name or NULL
 126  * @times: new times or NULL
 127  * @flags: zero or more flags (only AT_SYMLINK_NOFOLLOW for the moment)
 128  *
 129  * If filename is NULL and dfd refers to an open file, then operate on
 130  * the file.  Otherwise look up filename, possibly using dfd as a
 131  * starting point.
 132  *
 133  * If times==NULL, set access and modification to current time,
 134  * must be owner or have write permission.
 135  * Else, update from *times, must be owner or super user.
 136  */
 137 long do_utimes(int dfd, const char __user *filename, struct timespec *times,
 138                int flags)
 139 {
 140         int error = -EINVAL;
 141
 142         if (times && (!nsec_valid(times[0].tv_nsec) ||
 143                       !nsec_valid(times[1].tv_nsec))) {
 144                 goto out;
 145         }
 146
 147         if (flags & ~AT_SYMLINK_NOFOLLOW)
 148                 goto out;
 149
 150         if (filename == NULL && dfd != AT_FDCWD) {
 151                 struct fd f;
 152
 153                 if (flags & AT_SYMLINK_NOFOLLOW)
 154                         goto out;
 155
 156                 f = fdget(dfd);
 157                 error = -EBADF;
 158                 if (!f.file)
 159                         goto out;
 160
 161                 error = utimes_common(&f.file->f_path, times);
 162                 fdput(f);
 163         } else {
 164                 struct path path;
 165                 int lookup_flags = 0;
 166
 167                 if (!(flags & AT_SYMLINK_NOFOLLOW))
 168                         lookup_flags |= LOOKUP_FOLLOW;
 169 retry:
 170                 error = user_path_at(dfd, filename, lookup_flags, &path);
 171                 if (error)
 172                         goto out;
 173
 174                 error = utimes_common(&path, times);
 175                 path_put(&path);
 176                 if (retry_estale(error, lookup_flags)) {
 177                         lookup_flags |= LOOKUP_REVAL;
 178                         goto retry;
 179                 }
 180         }
 181
 182 out:
 183         return error;
 184 }
 185
 186 SYSCALL_DEFINE4(utimensat, int, dfd, const char __user *, filename,
 187                 struct timespec __user *, utimes, int, flags)
 188 {
 189         struct timespec tstimes[2];
 190
 191         if (utimes) {
 192                 if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
 193                         return -EFAULT;
 194
 195                 /* Nothing to do, we must not even check the path.  */
 196                 if (tstimes[0].tv_nsec == UTIME_OMIT &&
 197                     tstimes[1].tv_nsec == UTIME_OMIT)
 198                         return 0;
 199         }
 200
 201         return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
 202 }
 203
 204 SYSCALL_DEFINE3(futimesat, int, dfd, const char __user *, filename,
 205                 struct timeval __user *, utimes)
 206 {
 207         struct timeval times[2];
 208         struct timespec tstimes[2];
 209
 210         if (utimes) {
 211                 if (copy_from_user(&times, utimes, sizeof(times)))
 212                         return -EFAULT;
 213
 214                 /* This test is needed to catch all invalid values.  If we
 215                    would test only in do_utimes we would miss those invalid
 216                    values truncated by the multiplication with 1000.  Note
 217                    that we also catch UTIME_{NOW,OMIT} here which are only
 218                    valid for utimensat.  */
 219                 if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
 220                     times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
 221                         return -EINVAL;
 222
 223                 tstimes[0].tv_sec = times[0].tv_sec;
 224                 tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
 225                 tstimes[1].tv_sec = times[1].tv_sec;
 226                 tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
 227         }
 228
 229         return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
 230 }
 231
 232 SYSCALL_DEFINE2(utimes, char __user *, filename,
 233                 struct timeval __user *, utimes)
 234 {
 235         return sys_futimesat(AT_FDCWD, filename, utimes);
 236 }