Re: Oops with touch and unknown uid [was Re: 2.6.22-rc6-mm1]

Andrew Morton
2007-07-23T06:12:28Z

On Sun, 22 Jul 2007 23:48:14 +0200 "J.A. Magallón" <jamagallon@ono.com> wrote:

> On Thu, 28 Jun 2007 03:43:21 -0700, Andrew Morton <akpm@linux-foundation.org> wrote:
>
> >
> > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc6/2.6.22-rc6-mm1/
> >
>
> I have noticed a funny problem.
> Lets say 666 is not an uid used on you system. This oopses:
>
> rm -f dummy
> touch dummy
> chown 666 dummy
> touch dummy

Does Linus's fix fix it?

commit 1e5de2837c166535f9bb4232bfe97ea1f9fc7a1c
Author: Linus Torvalds <torvalds@woody.linux-foundation.org>
Date: Sun Jul 8 12:02:55 2007 -0700

Fix permission checking for the new utimensat() system call

Commit 1c710c896eb461895d3c399e15bb5f20b39c9073 added the utimensat()
system call, but didn't handle the case of checking for the writability
of the target right, when the target was a file descriptor, not a
filename.

We cannot use vfs_permission(MAY_WRITE) for that case, and need to
simply check whether the file descriptor is writable. The oops from
using the wrong function was noticed and narrowed down by Markus
Trippelsdorf.

Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Markus Trippelsdorf <markus@trippelsdorf.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Al Viro <viro@ftp.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/utimes.c b/fs/utimes.c
index 480f7c8..b3c8895 100644
--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -106,9 +106,16 @@ long do_utimes(int dfd, char __user *fil
if (IS_IMMUTABLE(inode))
goto dput_and_out;

- if (current->fsuid != inode->i_uid &&
- (error = vfs_permission(&nd, MAY_WRITE)) != 0)
- goto dput_and_out;
+ if (current->fsuid != inode->i_uid) {
+ if (f) {
+ if (!(f->f_mode & FMODE_WRITE))
+ goto dput_and_out;
+ } else {
+ error = vfs_permission(&nd, MAY_WRITE);
+ if (error)
+ goto dput_and_out;
+ }
+ }
}
mutex_lock(&inode->i_mutex);
error = notify_change(dentry, &newattrs);