[PATCH 5.10.y] libceph: fix OOB read in decode_watchers() via missing bounds check
Sasha Levin <[email protected]>
| Newsgroups | org.kernel.vger.stable |
|---|---|
| Message-ID | <[email protected]> |
From: Pavitra Jha <[email protected]> [ Upstream commit 00ead17c7de137a692edee59f2772e6af687e8eb ] 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 ] Cc: [email protected] Fixes: a4ed38d7a180 ("libceph: support for CEPH_OSD_OP_LIST_WATCHERS") Signed-off-by: Pavitra Jha <[email protected]> Reviewed-by: Viacheslav Dubeyko <[email protected]> Signed-off-by: Ilya Dryomov <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- 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 89b02b8baca35..92d379c60da5c 100644 --- a/net/ceph/osd_client.c +++ b/net/ceph/osd_client.c @@ -4993,7 +4993,7 @@ 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; @@ -5007,6 +5007,9 @@ static int decode_watchers(void **p, void *end, } return 0; + +bad: + return -EINVAL; } /* -- 2.53.0