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 asmlinkage long sys_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 /* If times==NULL, set access and modification to current time,
  52  * must be owner or have write permission.
  53  * Else, update from *times, must be owner or super user.
  54  */
  55 long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags)
  56 {
  57         int error;
  58         struct nameidata nd;
  59         struct dentry *dentry;
  60         struct inode *inode;
  61         struct iattr newattrs;
  62         struct file *f = NULL;
  63         struct vfsmount *mnt;
  64
  65         error = -EINVAL;
  66         if (times && (!nsec_valid(times[0].tv_nsec) ||
  67                       !nsec_valid(times[1].tv_nsec))) {
  68                 goto out;
  69         }
  70
  71         if (flags & ~AT_SYMLINK_NOFOLLOW)
  72                 goto out;
  73
  74         if (filename == NULL && dfd != AT_FDCWD) {
  75                 error = -EINVAL;
  76                 if (flags & AT_SYMLINK_NOFOLLOW)
  77                         goto out;
  78
  79                 error = -EBADF;
  80                 f = fget(dfd);
  81                 if (!f)
  82                         goto out;
  83                 dentry = f->f_path.dentry;
  84                 mnt = f->f_path.mnt;
  85         } else {
  86                 error = __user_walk_fd(dfd, filename, (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW, &nd);
  87                 if (error)
  88                         goto out;
  89
  90                 dentry = nd.path.dentry;
  91                 mnt = nd.path.mnt;
  92         }
  93
  94         inode = dentry->d_inode;
  95
  96         error = mnt_want_write(mnt);
  97         if (error)
  98                 goto dput_and_out;
  99
 100         if (times && times[0].tv_nsec == UTIME_NOW &&
 101                      times[1].tv_nsec == UTIME_NOW)
 102                 times = NULL;
 103
 104         /* In most cases, the checks are done in inode_change_ok() */
 105         newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
 106         if (times) {
 107                 error = -EPERM;
 108                 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
 109                         goto mnt_drop_write_and_out;
 110
 111                 if (times[0].tv_nsec == UTIME_OMIT)
 112                         newattrs.ia_valid &= ~ATTR_ATIME;
 113                 else if (times[0].tv_nsec != UTIME_NOW) {
 114                         newattrs.ia_atime.tv_sec = times[0].tv_sec;
 115                         newattrs.ia_atime.tv_nsec = times[0].tv_nsec;
 116                         newattrs.ia_valid |= ATTR_ATIME_SET;
 117                 }
 118
 119                 if (times[1].tv_nsec == UTIME_OMIT)
 120                         newattrs.ia_valid &= ~ATTR_MTIME;
 121                 else if (times[1].tv_nsec != UTIME_NOW) {
 122                         newattrs.ia_mtime.tv_sec = times[1].tv_sec;
 123                         newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
 124                         newattrs.ia_valid |= ATTR_MTIME_SET;
 125                 }
 126
 127                 /*
 128                  * For the UTIME_OMIT/UTIME_NOW and UTIME_NOW/UTIME_OMIT
 129                  * cases, we need to make an extra check that is not done by
 130                  * inode_change_ok().
 131                  */
 132                 if (((times[0].tv_nsec == UTIME_NOW &&
 133                             times[1].tv_nsec == UTIME_OMIT)
 134                      ||
 135                      (times[0].tv_nsec == UTIME_OMIT &&
 136                             times[1].tv_nsec == UTIME_NOW))
 137                     && !is_owner_or_cap(inode))
 138                         goto mnt_drop_write_and_out;
 139         } else {
 140
 141                 /*
 142                  * If times is NULL (or both times are UTIME_NOW),
 143                  * then we need to check permissions, because
 144                  * inode_change_ok() won't do it.
 145                  */
 146                 error = -EACCES;
 147                 if (IS_IMMUTABLE(inode))
 148                         goto mnt_drop_write_and_out;
 149
 150                 if (!is_owner_or_cap(inode)) {
 151                         error = permission(inode, MAY_WRITE, NULL);
 152                         if (error)
 153                                 goto mnt_drop_write_and_out;
 154                 }
 155         }
 156         mutex_lock(&inode->i_mutex);
 157         error = notify_change(dentry, &newattrs);
 158         mutex_unlock(&inode->i_mutex);
 159 mnt_drop_write_and_out:
 160         mnt_drop_write(mnt);
 161 dput_and_out:
 162         if (f)
 163                 fput(f);
 164         else
 165                 path_put(&nd.path);
 166 out:
 167         return error;
 168 }
 169
 170 asmlinkage long sys_utimensat(int dfd, char __user *filename, struct timespec __user *utimes, int flags)
 171 {
 172         struct timespec tstimes[2];
 173
 174         if (utimes) {
 175                 if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
 176                         return -EFAULT;
 177
 178                 /* Nothing to do, we must not even check the path.  */
 179                 if (tstimes[0].tv_nsec == UTIME_OMIT &&
 180                     tstimes[1].tv_nsec == UTIME_OMIT)
 181                         return 0;
 182         }
 183
 184         return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
 185 }
 186
 187 asmlinkage long sys_futimesat(int dfd, char __user *filename, struct timeval __user *utimes)
 188 {
 189         struct timeval times[2];
 190         struct timespec tstimes[2];
 191
 192         if (utimes) {
 193                 if (copy_from_user(&times, utimes, sizeof(times)))
 194                         return -EFAULT;
 195
 196                 /* This test is needed to catch all invalid values.  If we
 197                    would test only in do_utimes we would miss those invalid
 198                    values truncated by the multiplication with 1000.  Note
 199                    that we also catch UTIME_{NOW,OMIT} here which are only
 200                    valid for utimensat.  */
 201                 if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
 202                     times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
 203                         return -EINVAL;
 204
 205                 tstimes[0].tv_sec = times[0].tv_sec;
 206                 tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
 207                 tstimes[1].tv_sec = times[1].tv_sec;
 208                 tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
 209         }
 210
 211         return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
 212 }
 213
 214 asmlinkage long sys_utimes(char __user *filename, struct timeval __user *utimes)
 215 {
 216         return sys_futimesat(AT_FDCWD, filename, utimes);
 217 }