[PATCH 6.6.y] gfs2: Fix unlikely race in gdlm_put_lock

[Robert Garcia]

From: Andreas Gruenbacher <agruenba@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Reviewed-by: Andrew Price <anprice@xxxxxxxxxx>
[ Minor context change fixed. ]
Signed-off-by: Robert Garcia <rob_garcia@xxxxxxx>
---
 fs/gfs2/lock_dlm.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
index 07aac73377d8..a72ece097034 100644
--- a/fs/gfs2/lock_dlm.c
+++ b/fs/gfs2/lock_dlm.c
@@ -311,11 +311,6 @@ static void gdlm_put_lock(struct gfs2_glock *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 @@ static void gdlm_put_lock(struct gfs2_glock *gl)
 		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,
-- 
2.34.1