[PATCH v4] ceph: avoid putting the realm twice when decoding snaps fails

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From: Xiubo Li <xiubli@xxxxxxxxxx>

When decoding the snaps fails it maybe leaving the 'first_realm'
and 'realm' pointing to the same snaprealm memory. And then it'll
put it twice and could cause random use-after-free, BUG_ON, etc
issues.

Cc: stable@xxxxxxxxxxxxxxx
URL: https://tracker.ceph.com/issues/57686
Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
---

Changed in V4:
- remove initilizing of 'realm'.

 fs/ceph/snap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index 9bceed2ebda3..c1c452afa84d 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -764,7 +764,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
 	struct ceph_mds_snap_realm *ri;    /* encoded */
 	__le64 *snaps;                     /* encoded */
 	__le64 *prior_parent_snaps;        /* encoded */
-	struct ceph_snap_realm *realm = NULL;
+	struct ceph_snap_realm *realm;
 	struct ceph_snap_realm *first_realm = NULL;
 	struct ceph_snap_realm *realm_to_rebuild = NULL;
 	int rebuild_snapcs;
@@ -775,6 +775,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
 
 	dout("%s deletion=%d\n", __func__, deletion);
 more:
+	realm = NULL;
 	rebuild_snapcs = 0;
 	ceph_decode_need(&p, e, sizeof(*ri), bad);
 	ri = p;
-- 
2.31.1




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