[PATCH 6.6 152/175] gfs2: Fix unlikely race in gdlm_put_lock

Greg Kroah-Hartman
2026-03-31T16:31:28Z

From: Andreas Gruenbacher <agruenba@redhat.com>

[ Upstream commit 28c4d9bc0708956c1a736a9e49fee71b65deee81 ]

In gdlm_put_lock(), there is a small window of time in which the
DFL_UNMOUNT flag has been set but the lockspace hasn't been released,
yet. In that window, dlm may still call gdlm_ast() and gdlm_bast().
To prevent it from dereferencing freed glock objects, only free the
glock if the lockspace has actually been released.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Andrew Price <anprice@redhat.com>
[ Minor context change fixed. ]
Signed-off-by: Robert Garcia <rob_garcia@163.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/gfs2/lock_dlm.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

--- a/fs/gfs2/lock_dlm.c
+++ b/fs/gfs2/lock_dlm.c
@@ -311,11 +311,6 @@ static void gdlm_put_lock(struct gfs2_gl
gfs2_sbstats_inc(gl, GFS2_LKS_DCOUNT);
gfs2_update_request_times(gl);

- /* don't want to call dlm if we've unmounted the lock protocol */
- if (test_bit(DFL_UNMOUNT, &ls->ls_recover_flags)) {
- gfs2_glock_free(gl);
- return;
- }
/* don't want to skip dlm_unlock writing the lvb when lock has one */

if (test_bit(SDF_SKIP_DLM_UNLOCK, &sdp->sd_flags) &&
@@ -332,6 +327,11 @@ again:
goto again;
}

+ if (error == -ENODEV) {
+ gfs2_glock_free(gl);
+ return;
+ }
+
if (error) {
fs_err(sdp, "gdlm_unlock %x,%llx err=%d\n",
gl->gl_name.ln_type,