On Wed, 2007-04-11 at 14:13 -0400, Jeff Mahoney wrote:
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> Ian Kent wrote:
> > 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.
> >
>
> Ok, that was quick. I thought it was ok, but was about to dig back in to
> make sure. :)
Ya .. I'll think about it some more but it looks good.
Thanks again.
>
> - -Jeff
>
> - --
> Jeff Mahoney
> SUSE Labs
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