ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
Summary
| CVE | CVE-2026-89655 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-11 20:19:51 UTC |
| Updated | 2026-09-11 20:19:51 UTC |
| Description | In the Linux kernel, the following vulnerability has been resolved: ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock list_for_each_entry() iterates ci->i_cap_flush_list but drops i_ceph_lock to send cap messages. During the unlock window, handle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries with tid <= flush_tid from the list, release i_ceph_lock, and free them via ceph_free_cap_flush() outside any lock. When the original thread reacquires i_ceph_lock and the for-loop macro advances via cf = list_next_entry(cf, i_list), it dereferences cf->i_list.next on freed memory. The race timeline: __kick_flushing_caps() handle_cap_flush_ack() ----------------------- ----------------------- holds i_ceph_lock <--- iterates to cf (tid=10) prepares FLUSH message drops i_ceph_lock <--- __send_cap() ── FLUSH(tid=10) MDS sends FLUSH_ACK(tid=10) ---> acquires i_ceph_lock cf->tid(10) <= flush_tid(10), detaches cf from i_cap_flush_list drops i_ceph_lock ceph_free_cap_flush(cf) <- frees it! acquires i_ceph_lock <--- for-loop advances: cf = list_next_entry(cf, i_list) -- UAF on freed cf->i_list.next The cf was just sent by __kick_flushing_caps itself via __send_cap(). The MDS may respond with FLUSH_ACK quickly enough that handle_cap_flush_ack() frees cf before __kick_flushing_caps can finish the iteration. Fix by converting to a manual while loop: save the next pointer under i_ceph_lock before dropping it, then use the saved pointer after reacquiring, so the potentially-freed cf is never accessed again. |
Risk And Classification
EPSS: 0.002000000 probability, percentile 0.099720000 (date 2026-09-12)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 2701431aa3cc8b23efe6890182e7b04f5e76fab5 git | Not specified |
| CNA | Linux | Linux | affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 fe46746087b5b9c5bb2d022df6c7819218494ced git | Not specified |
| CNA | Linux | Linux | affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 2dba24dcd5050be4b7b119e6f0b01f62203b5d26 git | Not specified |
| CNA | Linux | Linux | affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 7af4c4f01305b0935adf6d4301b1ec407025485d git | Not specified |
| CNA | Linux | Linux | affected 6.12.109 semver | Not specified |
| CNA | Linux | Linux | affected 6.18.50 semver | Not specified |
| CNA | Linux | Linux | affected 7.2.4 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.109 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.50 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.2.4 7.2.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.3-rc1 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/2701431aa3cc8b23efe6890182e7b04f5e76fab5 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/7af4c4f01305b0935adf6d4301b1ec407025485d | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/fe46746087b5b9c5bb2d022df6c7819218494ced | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/2dba24dcd5050be4b7b119e6f0b01f62203b5d26 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.