From: Bryam Vargas <hexlabsecurity@proton.me> mainline inclusion from mainline-v7.2-rc5 commit 4dbc71bcaf9a30abf3920a4e2cc4ed33bba78c02 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/16967 CVE: CVE-2026-68160 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- ceph_handle_caps() reads snap_trace_len from the wire-format ceph_mds_caps header and uses it unconditionally to build a fake end pointer (snaptrace + snaptrace_len) that is later handed to ceph_update_snap_trace() in the CEPH_CAP_OP_IMPORT case: snaptrace = h + 1; snaptrace_len = le32_to_cpu(h->snap_trace_len); p = snaptrace + snaptrace_len; ... case CEPH_CAP_OP_IMPORT: if (snaptrace_len) { ... if (ceph_update_snap_trace(mdsc, snaptrace, snaptrace + snaptrace_len, false, &realm)) { ... } ceph_update_snap_trace() then decodes a struct ceph_mds_snap_realm from snaptrace using ceph_decode_need(&p, e, sizeof(*ri), bad) with the attacker-supplied fake end e == snaptrace + snaptrace_len. With snaptrace_len == 0xFFFFFFFF the bound check is trivially satisfied, ri = p reads sizeof(struct ceph_mds_snap_realm) past the legitimate msg->front buffer, and ri->num_snaps / ri->num_prior_parent_snaps then drive further out-of-bounds reads of the encoded snap arrays. The eleven msg_version >= 2 .. msg_version >= 12 decoder blocks above the op switch each catch this OOB through their ceph_decode_*_safe() / ceph_decode_need() helpers, but they sit behind a hdr.version-gated if, so a malicious or compromised MDS that sets msg->hdr.version = 1 reaches the IMPORT path with no version-gated decoder having validated snap_trace_len. The shape has been present since ceph_handle_caps() was introduced. Validate snap_trace_len against the message front buffer before consuming it, using the canonical ceph_decode_need() / ceph_has_room() helper. The helper bounds the length with subtraction (n <= end - p, guarded by end >= p) rather than pointer addition, so it is wrap-safe for the attacker-controlled u32 length on 32-bit builds where p + snap_trace_len could overflow the address space. This matches the rest of the ceph decode path (e.g. the pool_ns_len check a few lines below), and the existing goto bad cleanup already covers this exit path. Cc: stable@vger.kernel.org Fixes: a8599bd821d0 ("ceph: capability management") Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me> Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Conflicts: fs/ceph/caps.c [Context conflicts unmerged commit 8ea412e18131 ("ceph: improve caps debugging output")] Signed-off-by: Pan Taixi <pantaixi1@huawei.com> --- fs/ceph/caps.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index 8c1dd9e80e7e..31e5d87ec945 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -4124,10 +4124,11 @@ void ceph_handle_caps(struct ceph_mds_session *session, seq = le32_to_cpu(h->seq); mseq = le32_to_cpu(h->migrate_seq); snaptrace = h + 1; snaptrace_len = le32_to_cpu(h->snap_trace_len); + ceph_decode_need(&snaptrace, end, snaptrace_len, bad); p = snaptrace + snaptrace_len; if (msg_version >= 2) { u32 flock_len; ceph_decode_32_safe(&p, end, flock_len, bad); -- 2.34.1