From 824e0c3dd722e28cd57b61553026e5fb761e3895 Mon Sep 17 00:00:00 2001 From: Pavitra Jha Date: Wed, 8 Jul 2026 01:39:41 -0400 Subject: [PATCH] libceph: fix OOB read in decode_watchers() via missing bounds check ANBZ: #44683 commit 00ead17c7de137a692edee59f2772e6af687e8eb upstream. ceph_start_decoding() validates that struct_len bytes remain in the buffer after the encoding header, but accepts struct_len=0 as valid: ceph_decode_need(p, end, 0, bad) always passes. When a malicious or compromised OSD sends an obj_list_watch_response_t reply with struct_len=0, ceph_start_decoding() returns success with p == end, leaving zero bytes guaranteed for subsequent reads. The immediately following ceph_decode_32(p) in decode_watchers() has no preceding bounds check. With p == end this is a 4-byte read past the validated buffer boundary. The garbage value is then passed directly to kzalloc_objs() as the watcher count. The sibling function decode_watcher() already uses the safe variants (ceph_decode_copy_safe, ceph_decode_64_safe, ceph_decode_skip_32) after its own ceph_start_decoding() call. decode_watchers() is the only site that uses the bare variant, confirming an oversight. Fix by replacing ceph_decode_32(p) with ceph_decode_32_safe(p, end, *num_watchers, bad), consistent with the established pattern. Attacker model: a malicious or compromised OSD in a multi-tenant Ceph deployment (e.g. cloud) can trigger this against any kernel client that calls CEPH_OSD_OP_LIST_WATCHERS, without any further privileges beyond OSD session establishment. [ idryomov: trim changelog ] [backport-note] PatchPilot-Conflict-Type: context_drift Cc: stable@vger.kernel.org Fixes: a4ed38d7a180 ("libceph: support for CEPH_OSD_OP_LIST_WATCHERS") Signed-off-by: Pavitra Jha Reviewed-by: Viacheslav Dubeyko Signed-off-by: Ilya Dryomov Fixes: CVE-2026-80557 Assisted-by: PatchPilot Signed-off-by: D. Wythe --- net/ceph/osd_client.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c index d594cd501861..404d4b851d3f 100644 --- a/net/ceph/osd_client.c +++ b/net/ceph/osd_client.c @@ -4986,7 +4986,7 @@ static int decode_watchers(void **p, void *end, if (ret) return ret; - *num_watchers = ceph_decode_32(p); + ceph_decode_32_safe(p, end, *num_watchers, bad); *watchers = kcalloc(*num_watchers, sizeof(**watchers), GFP_NOIO); if (!*watchers) return -ENOMEM; @@ -5000,6 +5000,9 @@ static int decode_watchers(void **p, void *end, } return 0; + +bad: + return -EINVAL; } /* -- Gitee