[Cluster-devel] [PATCH GFS2] Fix kernel NULL pointer dereference by dlm_astd

[Bob Peterson <rpeterso@redhat.com>]

----- "Steven Whitehouse" <swhiteho@redhat.com> wrote:
| Hi,
| 
| Now in the -nmw GFS2 tree. Thanks,
| 
| Steve.
| 
| On Tue, 2010-06-15 at 12:07 -0400, Bob Peterson wrote:
| > Hi,
| > 
| > This patch fixes a problem in an error path when looking
| > up dinodes.  There are two sister-functions, gfs2_inode_lookup
| > and gfs2_process_unlinked_inode.  Both functions acquire and
| > hold the i_iopen glock for the dinode being looked up. The last
| > thing they try to do is hold the i_gl glock for the dinode.
| > If that glock fails for some reason, the error path was
| > incorrectly calling gfs2_glock_put for the i_iopen glock twice.
| > This resulted in the glock being prematurely freed.  The
| > "minimum hold time" usually kept the glock in memory, but the
| > lock interface to dlm (aka lock_dlm) freed its memory for the
| > glock.  In some circumstances, it would cause dlm's dlm_astd daemon
| > to try to call the bast function for the freed lock_dlm memory,
| > which resulted in a NULL pointer dereference.
| > 
| > This problem was discovered while testing bugzilla bug #595397.
| > 
| > Regards,
| > 
| > Bob Peterson
| > Red Hat GFS

Hi,

Actually, it's not yet in the -nmw git tree.  I think Steve W.
forgot to push it before he left on holiday.  At any rate, that's a
good thing because my testing has uncovered a possible problem
with this patch.  I'm planning to rework it and re-post when
I get a stable version.

Regards,

Bob Peterson
Red Hat File Systems