Root/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 */
27SYSCALL_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
43static 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
51static 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 (!is_owner_or_cap(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
108mnt_drop_write_and_out:
109    mnt_drop_write(path->mnt);
110out:
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 */
129long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags)
130{
131    int error = -EINVAL;
132
133    if (times && (!nsec_valid(times[0].tv_nsec) ||
134              !nsec_valid(times[1].tv_nsec))) {
135        goto out;
136    }
137
138    if (flags & ~AT_SYMLINK_NOFOLLOW)
139        goto out;
140
141    if (filename == NULL && dfd != AT_FDCWD) {
142        struct file *file;
143
144        if (flags & AT_SYMLINK_NOFOLLOW)
145            goto out;
146
147        file = fget(dfd);
148        error = -EBADF;
149        if (!file)
150            goto out;
151
152        error = utimes_common(&file->f_path, times);
153        fput(file);
154    } else {
155        struct path path;
156        int lookup_flags = 0;
157
158        if (!(flags & AT_SYMLINK_NOFOLLOW))
159            lookup_flags |= LOOKUP_FOLLOW;
160
161        error = user_path_at(dfd, filename, lookup_flags, &path);
162        if (error)
163            goto out;
164
165        error = utimes_common(&path, times);
166        path_put(&path);
167    }
168
169out:
170    return error;
171}
172
173SYSCALL_DEFINE4(utimensat, int, dfd, char __user *, filename,
174        struct timespec __user *, utimes, int, flags)
175{
176    struct timespec tstimes[2];
177
178    if (utimes) {
179        if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
180            return -EFAULT;
181
182        /* Nothing to do, we must not even check the path. */
183        if (tstimes[0].tv_nsec == UTIME_OMIT &&
184            tstimes[1].tv_nsec == UTIME_OMIT)
185            return 0;
186    }
187
188    return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
189}
190
191SYSCALL_DEFINE3(futimesat, int, dfd, char __user *, filename,
192        struct timeval __user *, utimes)
193{
194    struct timeval times[2];
195    struct timespec tstimes[2];
196
197    if (utimes) {
198        if (copy_from_user(&times, utimes, sizeof(times)))
199            return -EFAULT;
200
201        /* This test is needed to catch all invalid values. If we
202           would test only in do_utimes we would miss those invalid
203           values truncated by the multiplication with 1000. Note
204           that we also catch UTIME_{NOW,OMIT} here which are only
205           valid for utimensat. */
206        if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
207            times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
208            return -EINVAL;
209
210        tstimes[0].tv_sec = times[0].tv_sec;
211        tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
212        tstimes[1].tv_sec = times[1].tv_sec;
213        tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
214    }
215
216    return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
217}
218
219SYSCALL_DEFINE2(utimes, char __user *, filename,
220        struct timeval __user *, utimes)
221{
222    return sys_futimesat(AT_FDCWD, filename, utimes);
223}
224

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