From: Bob Peterson rpeterso@redhat.com
commit 78178ca844f0eb88f21f31c7fde969384be4c901 upstream.
Patch fb6791d100d1 was designed to allow gfs2 to unmount quicker by skipping the step where it tells dlm to unlock glocks in EX with lvbs. This was done because when gfs2 unmounts a file system, it destroys the dlm lockspace shortly after it destroys the glocks so it doesn't need to unlock them all: the unlock is implied when the lockspace is destroyed by dlm.
However, that patch introduced a use-after-free in dlm: as part of its normal dlm_recoverd process, it can call ls_recovery to recover dead locks. In so doing, it can call recover_rsbs which calls recover_lvb for any mastered rsbs. Func recover_lvb runs through the list of lkbs queued to the given rsb (if the glock is cached but unlocked, it will still be queued to the lkb, but in NL--Unlocked--mode) and if it has an lvb, copies it to the rsb, thus trying to preserve the lkb. However, when gfs2 skips the dlm unlock step, it frees the glock and its lvb, which means dlm's function recover_lvb references the now freed lvb pointer, copying the freed lvb memory to the rsb.
This patch changes the check in gdlm_put_lock so that it calls dlm_unlock for all glocks that contain an lvb pointer.
Fixes: fb6791d100d1 ("GFS2: skip dlm_unlock calls in unmount") Cc: stable@vger.kernel.org # v3.8+ Signed-off-by: Bob Peterson rpeterso@redhat.com Signed-off-by: Andreas Gruenbacher agruenba@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/gfs2/lock_dlm.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
--- a/fs/gfs2/lock_dlm.c +++ b/fs/gfs2/lock_dlm.c @@ -280,7 +280,6 @@ static void gdlm_put_lock(struct gfs2_gl { struct gfs2_sbd *sdp = gl->gl_name.ln_sbd; struct lm_lockstruct *ls = &sdp->sd_lockstruct; - int lvb_needs_unlock = 0; int error;
if (gl->gl_lksb.sb_lkid == 0) { @@ -293,13 +292,10 @@ static void gdlm_put_lock(struct gfs2_gl gfs2_sbstats_inc(gl, GFS2_LKS_DCOUNT); gfs2_update_request_times(gl);
- /* don't want to skip dlm_unlock writing the lvb when lock is ex */ - - if (gl->gl_lksb.sb_lvbptr && (gl->gl_state == LM_ST_EXCLUSIVE)) - lvb_needs_unlock = 1; + /* don't want to skip dlm_unlock writing the lvb when lock has one */
if (test_bit(SDF_SKIP_DLM_UNLOCK, &sdp->sd_flags) && - !lvb_needs_unlock) { + !gl->gl_lksb.sb_lvbptr) { gfs2_glock_free(gl); return; }