Re: [PATCH] vfs: fix race in rcu lookup of pruned dentry

Al Viro
2011-07-19T23:55:20Z

On Wed, Jul 20, 2011 at 12:52:16AM +0100, Al Viro wrote:
> On Wed, Jul 20, 2011 at 12:45:51AM +0100, Al Viro wrote:
>
> > You know what... I doubt that you want to mess with ->d_seq checks here.
> > It's definitely not Hugh's bug (unless he has bindings somewhere odd) and
> > both ->mnt_mountpoint and ->mnt_root are pinned (and we are holding
> > vfsmount_lock anyway). *inode assignment too early is a real bug, indeed,
> > and we want to assign nd->seq if we cross mountpoint as both versions do,
> > but check just before that is, in the best case, BUG_ON() fodder. We'd
> > just found a vfsmount with ->mnt_mountpoint equal to path->dentry; it *can't*
> > be stale, or we have a really nasty problem anyway.
>
> Kudos to neilb for spotting the pointless check, BTW; and no, his theory
> that it might be needed since we could race with umount() is wrong - due to
> vfsmount_lock being held.

Updated, pushed. Please, pull from the usual place (
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6.git/ for-linus
).

Shortlog:
Al Viro (1):
Fix cifs_get_root()

Linus Torvalds (1):
vfs: fix race in rcu lookup of pruned dentry

Diffstat:
fs/cifs/cifsfs.c | 100 +++++++++++++++--------------------------------------
fs/namei.c | 10 +++++-
2 files changed, 38 insertions(+), 72 deletions(-)