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CVE-2026-89655

ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: total

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From e4500b5e35c213e0f97be7cb69328c0877203a79 · fixed in 091137821e1fc88f37e15201abf055c9494ddc61; From e4500b5e35c213e0f97be7cb69328c0877203a79 · fixed in 01542430081014d80fc9e70e92d6647432ddb7fc; From e4500b5e35c213e0f97be7cb69328c0877203a79 · fixed in 23eb34a53a53cb1a6dab1eeee830633207ac158d; From e4500b5e35c213e0f97be7cb69328c0877203a79 · fixed in 19f16f04c2b014a7dd214dc1e42557d8530b16f3; From e4500b5e35c213e0f97be7cb69328c0877203a79 · fixed in 2701431aa3cc8b23efe6890182e7b04f5e76fab5; From e4500b5e35c213e0f97be7cb69328c0877203a79 · fixed in fe46746087b5b9c5bb2d022df6c7819218494ced; From e4500b5e35c213e0f97be7cb69328c0877203a79 · fixed in 2dba24dcd5050be4b7b119e6f0b01f62203b5d26; From e4500b5e35c213e0f97be7cb69328c0877203a79 · fixed in 7af4c4f01305b0935adf6d4301b1ec407025485d

  • Linux Linux

    4.8

  • KernelLinux

    From 4.8.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.109; From 6.13.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 8

git.kernel.org