[patch 1/4] vfs: utimes: move owner check into inode_change_ok()

Add a new ia_valid flag: ATTR_TIMES_SET, to handle the
UTIMES_OMIT/UTIMES_NOW and UTIMES_NOW/UTIMES_OMIT cases.  In these
cases neither ATTR_MTIME_SET nor ATTR_ATIME_SET is in the flags, yet
the POSIX draft specifies that permission checking is performed the
same way as if one or both of the times was explicitly set to a
timestamp.

See the path "vfs: utimensat(): fix error checking for
{UTIME_NOW,UTIME_OMIT} case" by Michael Kerrisk for the patch
introducing this behavior.

This is a cleanup, as well as allowing filesystems (NFS/fuse/...) to
perform their own permission checking instead of the default.

CC: Ulrich Drepper <drepper@redhat.com>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 22 insertions, 30 deletions

diff --git a/fs/attr.c b/fs/attr.c
index 966b73e25f82..765fc75fab3b 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -51,7 +51,7 @@ int inode_change_ok(struct inode *inode, struct iattr *attr)
         }
 
         /* Check for setting the inode time. */
-        if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET)) {
+        if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
                 if (!is_owner_or_cap(inode))
                         goto error;
         }
diff --git a/fs/utimes.c b/fs/utimes.c
index b6b664e7145e..ecf8941ba34a 100644
--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -101,7 +101,6 @@ long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags
                      times[1].tv_nsec == UTIME_NOW)
                 times = NULL;
 
-        /* In most cases, the checks are done in inode_change_ok() */
         newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
         if (times) {
                 error = -EPERM;
@@ -123,21 +122,13 @@ long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags
                         newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
                         newattrs.ia_valid |= ATTR_MTIME_SET;
                 }
-
                 /*
-                 * For the UTIME_OMIT/UTIME_NOW and UTIME_NOW/UTIME_OMIT
-                 * cases, we need to make an extra check that is not done by
-                 * inode_change_ok().
+                 * Tell inode_change_ok(), that this is an explicit time
+                 * update, even if neither ATTR_ATIME_SET nor ATTR_MTIME_SET
+                 * were used.
                  */
-                if (((times[0].tv_nsec == UTIME_NOW &&
-                            times[1].tv_nsec == UTIME_OMIT)
-                     ||
-                     (times[0].tv_nsec == UTIME_OMIT &&
-                            times[1].tv_nsec == UTIME_NOW))
-                    && !is_owner_or_cap(inode))
-                        goto mnt_drop_write_and_out;
+                newattrs.ia_valid |= ATTR_TIMES_SET;
         } else {
-
                 /*
                  * If times is NULL (or both times are UTIME_NOW),
                  * then we need to check permissions, because
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d8721e818b45..527b9e482f99 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -320,22 +320,23 @@ typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
  * Attribute flags.  These should be or-ed together to figure out what
  * has been changed!
  */
-#define ATTR_MODE       1
-#define ATTR_UID        2
-#define ATTR_GID        4
-#define ATTR_SIZE       8
-#define ATTR_ATIME      16
-#define ATTR_MTIME      32
-#define ATTR_CTIME      64
-#define ATTR_ATIME_SET  128
-#define ATTR_MTIME_SET  256
-#define ATTR_FORCE      512     /* Not a change, but a change it */
-#define ATTR_ATTR_FLAG  1024
-#define ATTR_KILL_SUID  2048
-#define ATTR_KILL_SGID  4096
-#define ATTR_FILE       8192
-#define ATTR_KILL_PRIV  16384
-#define ATTR_OPEN       32768   /* Truncating from open(O_TRUNC) */
+#define ATTR_MODE       (1 << 0)
+#define ATTR_UID        (1 << 1)
+#define ATTR_GID        (1 << 2)
+#define ATTR_SIZE       (1 << 3)
+#define ATTR_ATIME      (1 << 4)
+#define ATTR_MTIME      (1 << 5)
+#define ATTR_CTIME      (1 << 6)
+#define ATTR_ATIME_SET  (1 << 7)
+#define ATTR_MTIME_SET  (1 << 8)
+#define ATTR_FORCE      (1 << 9) /* Not a change, but a change it */
+#define ATTR_ATTR_FLAG  (1 << 10)
+#define ATTR_KILL_SUID  (1 << 11)
+#define ATTR_KILL_SGID  (1 << 12)
+#define ATTR_FILE       (1 << 13)
+#define ATTR_KILL_PRIV  (1 << 14)
+#define ATTR_OPEN       (1 << 15) /* Truncating from open(O_TRUNC) */
+#define ATTR_TIMES_SET  (1 << 16)
 
 /*
  * This is the Inode Attributes structure, used for notify_change().  It