From: Pavitra Jha Date: Tue, 2 Jun 2026 04:17:35 +0000 (-0400) Subject: libceph: fix two unsafe bare decodes in decode_lockers() X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=a109a556115271ca7896dcda7b4b7e45e156c227;p=thirdparty%2Fkernel%2Flinux.git libceph: fix two unsafe bare decodes in decode_lockers() decode_lockers() in cls_lock_client.c contains two bare decode operations that allow a malicious or compromised OSD to trigger slab-out-of-bounds reads: 1. ceph_decode_32(p) at the num_lockers field has no preceding bounds check. ceph_start_decoding() accepts struct_len=0 as valid -- the internal ceph_decode_need(p, end, 0, bad) always passes -- so when an OSD sends struct_len=0, ceph_start_decoding() returns success with p == end. The immediately following bare ceph_decode_32(p) then reads 4 bytes past the validated buffer boundary. The garbage value is passed directly to kzalloc_objs() as the locker count. The sibling function decode_watchers() in osd_client.c already uses ceph_decode_32_safe() after its own ceph_start_decoding() call. decode_lockers() was the only site using the bare variant. 2. ceph_decode_8(p) after the decode_locker() loop has no preceding bounds check. If an OSD crafts num_lockers such that the loop advances p exactly to end, the subsequent bare ceph_decode_8(p) reads one byte past the validated buffer boundary. The result is passed directly into *type, which is used as a lock type discriminator by callers, giving an OSD-controlled one-byte OOB read with direct influence over the lock type field. Fix both by replacing bare operations with their safe variants: ceph_decode_32(p) -> ceph_decode_32_safe(p, end, *num_lockers, err_inval) ceph_decode_8(p) -> ceph_decode_8_safe(p, end, *type, err_free_lockers) The goto targets differ intentionally: err_inval: is a new label returning -EINVAL directly. It is used for the pre-allocation failure path where *lockers is not yet allocated and must not be passed to ceph_free_lockers(). err_free_lockers: is the existing label. It is used for the post-allocation failure path where *lockers is allocated and must be freed. ret is set to -EINVAL before ceph_decode_8_safe() so that err_free_lockers returns the correct error code on bounds violation. Without this, err_free_lockers would return a stale ret value (0 from the successful decode_locker() loop), silently swallowing the error. -EINVAL is correct for both failure paths. The data received from the OSD is structurally malformed. -ENOMEM would misrepresent the failure class to callers and to stable@ backporters triaging error paths. Attacker model: a malicious or compromised OSD in a multi-tenant Ceph deployment can trigger this against any kernel client that issues the lock.get_info class method (e.g. during RBD exclusive lock acquisition). [ idryomov: trim changelog, formatting ] Cc: stable@vger.kernel.org Fixes: d4ed4a530562 ("libceph: support for lock.lock_info") Signed-off-by: Pavitra Jha Reviewed-by: Viacheslav Dubeyko Signed-off-by: Ilya Dryomov --- diff --git a/net/ceph/cls_lock_client.c b/net/ceph/cls_lock_client.c index c6956f1df333..377336982f7d 100644 --- a/net/ceph/cls_lock_client.c +++ b/net/ceph/cls_lock_client.c @@ -299,7 +299,7 @@ static int decode_lockers(void **p, void *end, u8 *type, char **tag, if (ret) return ret; - *num_lockers = ceph_decode_32(p); + ceph_decode_32_safe(p, end, *num_lockers, err_inval); *lockers = kzalloc_objs(**lockers, *num_lockers, GFP_NOIO); if (!*lockers) return -ENOMEM; @@ -310,7 +310,8 @@ static int decode_lockers(void **p, void *end, u8 *type, char **tag, goto err_free_lockers; } - *type = ceph_decode_8(p); + ret = -EINVAL; + ceph_decode_8_safe(p, end, *type, err_free_lockers); s = ceph_extract_encoded_string(p, end, NULL, GFP_NOIO); if (IS_ERR(s)) { ret = PTR_ERR(s); @@ -320,6 +321,9 @@ static int decode_lockers(void **p, void *end, u8 *type, char **tag, *tag = s; return 0; +err_inval: + return -EINVAL; + err_free_lockers: ceph_free_lockers(*lockers, *num_lockers); return ret;