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TOMOYO Linux Cross Reference
Linux/fs/utimes.c

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  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 file *file;
144 
145                 if (flags & AT_SYMLINK_NOFOLLOW)
146                         goto out;
147 
148                 file = fget(dfd);
149                 error = -EBADF;
150                 if (!file)
151                         goto out;
152 
153                 error = utimes_common(&file->f_path, times);
154                 fput(file);
155         } else {
156                 struct path path;
157                 int lookup_flags = 0;
158 
159                 if (!(flags & AT_SYMLINK_NOFOLLOW))
160                         lookup_flags |= LOOKUP_FOLLOW;
161 
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         }
169 
170 out:
171         return error;
172 }
173 
174 SYSCALL_DEFINE4(utimensat, int, dfd, const char __user *, filename,
175                 struct timespec __user *, utimes, int, flags)
176 {
177         struct timespec tstimes[2];
178 
179         if (utimes) {
180                 if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
181                         return -EFAULT;
182 
183                 /* Nothing to do, we must not even check the path.  */
184                 if (tstimes[0].tv_nsec == UTIME_OMIT &&
185                     tstimes[1].tv_nsec == UTIME_OMIT)
186                         return 0;
187         }
188 
189         return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
190 }
191 
192 SYSCALL_DEFINE3(futimesat, int, dfd, const char __user *, filename,
193                 struct timeval __user *, utimes)
194 {
195         struct timeval times[2];
196         struct timespec tstimes[2];
197 
198         if (utimes) {
199                 if (copy_from_user(&times, utimes, sizeof(times)))
200                         return -EFAULT;
201 
202                 /* This test is needed to catch all invalid values.  If we
203                    would test only in do_utimes we would miss those invalid
204                    values truncated by the multiplication with 1000.  Note
205                    that we also catch UTIME_{NOW,OMIT} here which are only
206                    valid for utimensat.  */
207                 if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
208                     times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
209                         return -EINVAL;
210 
211                 tstimes[0].tv_sec = times[0].tv_sec;
212                 tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
213                 tstimes[1].tv_sec = times[1].tv_sec;
214                 tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
215         }
216 
217         return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
218 }
219 
220 SYSCALL_DEFINE2(utimes, char __user *, filename,
221                 struct timeval __user *, utimes)
222 {
223         return sys_futimesat(AT_FDCWD, filename, utimes);
224 }
225 

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