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 */
  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 (!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
 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, 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 fd f;
 144
 145                if (flags & AT_SYMLINK_NOFOLLOW)
 146                        goto out;
 147
 148                f = fdget(dfd);
 149                error = -EBADF;
 150                if (!f.file)
 151                        goto out;
 152
 153                error = utimes_common(&f.file->f_path, times);
 154                fdput(f);
 155        } else {
 156                struct path path;
 157                int lookup_flags = 0;
 158
 159                if (!(flags & AT_SYMLINK_NOFOLLOW))
 160                        lookup_flags |= LOOKUP_FOLLOW;
 161retry:
 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                if (retry_estale(error, lookup_flags)) {
 169                        lookup_flags |= LOOKUP_REVAL;
 170                        goto retry;
 171                }
 172        }
 173
 174out:
 175        return error;
 176}
 177
 178SYSCALL_DEFINE4(utimensat, int, dfd, const char __user *, filename,
 179                struct timespec __user *, utimes, int, flags)
 180{
 181        struct timespec tstimes[2];
 182
 183        if (utimes) {
 184                if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
 185                        return -EFAULT;
 186
 187                /* Nothing to do, we must not even check the path.  */
 188                if (tstimes[0].tv_nsec == UTIME_OMIT &&
 189                    tstimes[1].tv_nsec == UTIME_OMIT)
 190                        return 0;
 191        }
 192
 193        return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
 194}
 195
 196SYSCALL_DEFINE3(futimesat, int, dfd, const char __user *, filename,
 197                struct timeval __user *, utimes)
 198{
 199        struct timeval times[2];
 200        struct timespec tstimes[2];
 201
 202        if (utimes) {
 203                if (copy_from_user(&times, utimes, sizeof(times)))
 204                        return -EFAULT;
 205
 206                /* This test is needed to catch all invalid values.  If we
 207                   would test only in do_utimes we would miss those invalid
 208                   values truncated by the multiplication with 1000.  Note
 209                   that we also catch UTIME_{NOW,OMIT} here which are only
 210                   valid for utimensat.  */
 211                if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
 212                    times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
 213                        return -EINVAL;
 214
 215                tstimes[0].tv_sec = times[0].tv_sec;
 216                tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
 217                tstimes[1].tv_sec = times[1].tv_sec;
 218                tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
 219        }
 220
 221        return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
 222}
 223
 224SYSCALL_DEFINE2(utimes, char __user *, filename,
 225                struct timeval __user *, utimes)
 226{
 227        return sys_futimesat(AT_FDCWD, filename, utimes);
 228}
 229
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