On Thu, 2007-04-12 at 02:00 +0800, Ian Kent wrote:
> On Thu, 2007-04-12 at 01:49 +0800, Ian Kent wrote:
> > On Wed, 2007-04-11 at 11:05 -0400, Jeff Mahoney wrote:
> > > Commit f50b6f8691cae2e0064c499dd3ef3f31142987f0 introduced a
> > > race in autofs4 between autofs_lookup_unhashed() and
> > > autofs_dentry_release().
> > >
> > > autofs_dentry_release() ends up clearing the ->dentry and ->inode
> > > members of autofs_info before removing it from the rehash list. The
> > > list is protected by the rehash lock in both functions, but
> > > since autofs_dentry_release() starts tearing the autofs_info struct
> > > down before removing it from the list, autofs_lookup_unhashed() can
> > > get a autofs_info with a NULL dentry.
> > >
> > > This patch moves the clearing of ->dentry and ->inode after the removal
> > > from the rehash list.
> >
> > Oh .. excellent, I had a bug report but I just couldn't see it for
> > looking.
>
> Maybe I've been a bit hasty with the celebration.
> It looks like I've got a bigger locking problem here.
> If autofs4_dentry_release waits on the rehash lock and
> autofs4_lookup_unhashed reclaims it then the info struct and the dentry
> go away unconditionally as the release is called just prior to freeing
> the dentry memory, right?.
No I'm wrong, dentry_iput holds the dcache locks till it sets d_inode to
NULL, the point of the d_inode check in autofs4_lookup_unhashed.
My day is still made.
> >
> > You've made my day.
> > Thanks heaps
> > Ian
> >
> > >
> > > Signed-off-by: Jeff Mahoney <[EMAIL PROTECTED]>
> > Acked-by: Ian Kent <[EMAIL PROTECTED]>
> >
> > >
> > > ---
> > >
> > > fs/autofs4/root.c | 6 +++---
> > > 1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > --- a/fs/autofs4/root.c 2007-04-11 09:41:44.000000000 -0400
> > > +++ b/fs/autofs4/root.c 2007-04-11 10:54:37.000000000 -0400
> > > @@ -470,9 +470,6 @@ void autofs4_dentry_release(struct dentr
> > > if (inf) {
> > > struct autofs_sb_info *sbi = autofs4_sbi(de->d_sb);
> > >
> > > - inf->dentry = NULL;
> > > - inf->inode = NULL;
> > > -
> > > if (sbi) {
> > > spin_lock(&sbi->rehash_lock);
> > > if (!list_empty(&inf->rehash))
> > > @@ -480,6 +477,9 @@ void autofs4_dentry_release(struct dentr
> > > spin_unlock(&sbi->rehash_lock);
> > > }
> > >
> > > + inf->dentry = NULL;
> > > + inf->inode = NULL;
> > > +
> > > autofs4_free_ino(inf);
> > > }
> > > }
> > >
-
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