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 setattr_prepare(), 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                  * setattr_prepare() won't do it.
  94                  */
  95                 error = -EACCES;
  96                 if (IS_IMMUTABLE(inode))
  97                         goto mnt_drop_write_and_out;
  98
  99                 if (!inode_owner_or_capable(inode)) {
 100                         error = inode_permission(inode, MAY_WRITE);
 101                         if (error)
 102                                 goto mnt_drop_write_and_out;
 103                 }
 104         }
 105 retry_deleg:
 106         mutex_lock(&inode->i_mutex);
 107         error = notify_change(path->dentry, &newattrs, &delegated_inode);
 108         mutex_unlock(&inode->i_mutex);
 109         if (delegated_inode) {
 110                 error = break_deleg_wait(&delegated_inode);
 111                 if (!error)
 112                         goto retry_deleg;
 113         }
 114
 115 mnt_drop_write_and_out:
 116         mnt_drop_write(path->mnt);
 117 out:
 118         return error;
 119 }
 120
 121 /*
 122  * do_utimes - change times on filename or file descriptor
 123  * @dfd: open file descriptor, -1 or AT_FDCWD
 124  * @filename: path name or NULL
 125  * @times: new times or NULL
 126  * @flags: zero or more flags (only AT_SYMLINK_NOFOLLOW for the moment)
 127  *
 128  * If filename is NULL and dfd refers to an open file, then operate on
 129  * the file.  Otherwise look up filename, possibly using dfd as a
 130  * starting point.
 131  *
 132  * If times==NULL, set access and modification to current time,
 133  * must be owner or have write permission.
 134  * Else, update from *times, must be owner or super user.
 135  */
 136 long do_utimes(int dfd, const char __user *filename, struct timespec *times,
 137                int flags)
 138 {
 139         int error = -EINVAL;
 140
 141         if (times && (!nsec_valid(times[0].tv_nsec) ||
 142                       !nsec_valid(times[1].tv_nsec))) {
 143                 goto out;
 144         }
 145
 146         if (flags & ~AT_SYMLINK_NOFOLLOW)
 147                 goto out;
 148
 149         if (filename == NULL && dfd != AT_FDCWD) {
 150                 struct fd f;
 151
 152                 if (flags & AT_SYMLINK_NOFOLLOW)
 153                         goto out;
 154
 155                 f = fdget(dfd);
 156                 error = -EBADF;
 157                 if (!f.file)
 158                         goto out;
 159
 160                 error = utimes_common(&f.file->f_path, times);
 161                 fdput(f);
 162         } else {
 163                 struct path path;
 164                 int lookup_flags = 0;
 165
 166                 if (!(flags & AT_SYMLINK_NOFOLLOW))
 167                         lookup_flags |= LOOKUP_FOLLOW;
 168 retry:
 169                 error = user_path_at(dfd, filename, lookup_flags, &path);
 170                 if (error)
 171                         goto out;
 172
 173                 error = utimes_common(&path, times);
 174                 path_put(&path);
 175                 if (retry_estale(error, lookup_flags)) {
 176                         lookup_flags |= LOOKUP_REVAL;
 177                         goto retry;
 178                 }
 179         }
 180
 181 out:
 182         return error;
 183 }
 184
 185 SYSCALL_DEFINE4(utimensat, int, dfd, const char __user *, filename,
 186                 struct timespec __user *, utimes, int, flags)
 187 {
 188         struct timespec tstimes[2];
 189
 190         if (utimes) {
 191                 if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
 192                         return -EFAULT;
 193
 194                 /* Nothing to do, we must not even check the path.  */
 195                 if (tstimes[0].tv_nsec == UTIME_OMIT &&
 196                     tstimes[1].tv_nsec == UTIME_OMIT)
 197                         return 0;
 198         }
 199
 200         return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
 201 }
 202
 203 SYSCALL_DEFINE3(futimesat, int, dfd, const char __user *, filename,
 204                 struct timeval __user *, utimes)
 205 {
 206         struct timeval times[2];
 207         struct timespec tstimes[2];
 208
 209         if (utimes) {
 210                 if (copy_from_user(&times, utimes, sizeof(times)))
 211                         return -EFAULT;
 212
 213                 /* This test is needed to catch all invalid values.  If we
 214                    would test only in do_utimes we would miss those invalid
 215                    values truncated by the multiplication with 1000.  Note
 216                    that we also catch UTIME_{NOW,OMIT} here which are only
 217                    valid for utimensat.  */
 218                 if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
 219                     times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
 220                         return -EINVAL;
 221
 222                 tstimes[0].tv_sec = times[0].tv_sec;
 223                 tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
 224                 tstimes[1].tv_sec = times[1].tv_sec;
 225                 tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
 226         }
 227
 228         return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
 229 }
 230
 231 SYSCALL_DEFINE2(utimes, char __user *, filename,
 232                 struct timeval __user *, utimes)
 233 {
 234         return sys_futimesat(AT_FDCWD, filename, utimes);
 235 }