[patch for 2.6.26 4/4] vfs: utimensat(): fix write access check for futimens()
[linux-3.10.git] / 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 }