[PATCH 4.19 042/105] ceph: avoid putting the realm twice when decoding snaps fails

Greg Kroah-Hartman
2022-12-05T19:19:37Z

From: Xiubo Li <xiubli@redhat.com>

[ Upstream commit 51884d153f7ec85e18d607b2467820a90e0f4359 ]

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@vger.kernel.org
Link: https://tracker.ceph.com/issues/57686
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 642040beef91..a5ef8275440d 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -671,7 +671,7 @@ 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;
@@ -680,6 +680,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,

dout("update_snap_trace deletion=%d\n", deletion);
more:
+ realm = NULL;
rebuild_snapcs = 0;
ceph_decode_need(&p, e, sizeof(*ri), bad);
ri = p;
--
2.35.1