From b3bf89767e3ca9506f1c7167cac97c41ec254d42 Mon Sep 17 00:00:00 2001 From: Xiang Mei Date: Tue, 15 Sep 2026 14:40:27 -0700 Subject: [PATCH] ceph: fix integer overflow in the snap trace bounds check ceph_update_snap_trace() bounds the two encoded snapid arrays that follow a struct ceph_mds_snap_realm with sizeof(u64) * (num_snaps + num_prior_parent_snaps). Both counts come straight off the wire as __le32, so the addition is evaluated in unsigned int and wraps before sizeof(u64) promotes it to size_t: an MDS sending num_snaps = 1 and num_prior_parent_snaps = 0xffffffff makes the sum zero and the check degenerates to ceph_decode_need(&p, e, 0, bad), which always passes. dup_array() then reads num_snaps * 8 bytes past the end of the message front, which ceph_msg_new2() allocates at exactly front_len bytes. An unsolicited CEPH_MSG_CLIENT_SNAP reaches this from a malicious or compromised MDS with no client-side action, as do the snaptraces carried in an MDS reply and in a cap import. Compute the length with size_add()/size_mul() so it saturates at SIZE_MAX instead of wrapping, in the style fs/ceph/mdsmap.c already uses for num_export_targets. BUG: KASAN: slab-out-of-bounds in dup_array (include/linux/unaligned.h:28 fs/ceph/snap.c:500) Read of size 8 at addr ffff8880102a16c8 by task kworker/1:2/129 Workqueue: ceph-msgr ceph_con_workfn Call Trace: dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120) print_report (mm/kasan/report.c:378 mm/kasan/report.c:482) kasan_report (mm/kasan/report.c:595) dup_array (include/linux/unaligned.h:28 fs/ceph/snap.c:500) ceph_update_snap_trace (fs/ceph/snap.c:836) ceph_handle_snap (fs/ceph/snap.c:1155) mds_dispatch (fs/ceph/mds_client.c:7234) ceph_con_process_message (net/ceph/messenger.c:1424) ceph_con_v1_try_read (net/ceph/messenger_v1.c:1430) ceph_con_workfn (net/ceph/messenger.c:1576) process_one_work (kernel/workqueue.c:3396) worker_thread (kernel/workqueue.c:3479 kernel/workqueue.c:3560) kthread (kernel/kthread.c:436) ret_from_fork (arch/x86/kernel/process.c:158) ret_from_fork_asm (arch/x86/entry/entry_64.S:245) ... The buggy address is located 0 bytes to the right of allocated 72-byte region [ffff8880102a1680, ffff8880102a16c8) Cc: stable@vger.kernel.org Fixes: 963b61eb041e ("ceph: snapshot management") Reported-by: co+ecaada42f806f629@bugs.sh Assisted-by: LLM Signed-off-by: Xiang Mei Reviewed-by: Alex Markuze Signed-off-by: Ilya Dryomov --- fs/ceph/snap.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c index 498ffc1a91cb..5c1540d95b8c 100644 --- a/fs/ceph/snap.c +++ b/fs/ceph/snap.c @@ -788,6 +788,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc, struct ceph_snap_realm *first_realm = NULL; struct ceph_snap_realm *realm_to_rebuild = NULL; struct ceph_client *client = mdsc->fsc->client; + size_t snaps_len; int rebuild_snapcs; int err = -ENOMEM; int ret; @@ -802,8 +803,10 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc, ceph_decode_need(&p, e, sizeof(*ri), bad); ri = p; p += sizeof(*ri); - ceph_decode_need(&p, e, sizeof(u64)*(le32_to_cpu(ri->num_snaps) + - le32_to_cpu(ri->num_prior_parent_snaps)), bad); + snaps_len = size_mul(size_add(le32_to_cpu(ri->num_snaps), + le32_to_cpu(ri->num_prior_parent_snaps)), + sizeof(u64)); + ceph_decode_need(&p, e, snaps_len, bad); snaps = p; p += sizeof(u64) * le32_to_cpu(ri->num_snaps); prior_parent_snaps = p;