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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. :)
- -Jeff
- --
Jeff Mahoney
SUSE Labs
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