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CVE PROGRAM SOURCE RECORD9.8 Critical

CVE-2026-89655

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

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Status
Published
Published
Updated
Assigning organization
Linux

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • e4500b5e35c213e0f97be7cb69328c0877203a79 to < 091137821e1fc88f37e15201abf055c9494ddc61affected
  • e4500b5e35c213e0f97be7cb69328c0877203a79 to < 01542430081014d80fc9e70e92d6647432ddb7fcaffected
  • e4500b5e35c213e0f97be7cb69328c0877203a79 to < 23eb34a53a53cb1a6dab1eeee830633207ac158daffected
  • e4500b5e35c213e0f97be7cb69328c0877203a79 to < 19f16f04c2b014a7dd214dc1e42557d8530b16f3affected
  • e4500b5e35c213e0f97be7cb69328c0877203a79 to < 2701431aa3cc8b23efe6890182e7b04f5e76fab5affected
  • e4500b5e35c213e0f97be7cb69328c0877203a79 to < fe46746087b5b9c5bb2d022df6c7819218494cedaffected
  • e4500b5e35c213e0f97be7cb69328c0877203a79 to < 2dba24dcd5050be4b7b119e6f0b01f62203b5d26affected
  • e4500b5e35c213e0f97be7cb69328c0877203a79 to < 7af4c4f01305b0935adf6d4301b1ec407025485daffected

Linux Linux

Default version status: affected

  • 4.8affected
  • 0 to < 4.8unaffected
  • 5.10.270 to ≤ 5.10.*unaffected
  • 5.15.221 to ≤ 5.15.*unaffected
  • 6.1.188 to ≤ 6.1.*unaffected
  • 6.6.157 to ≤ 6.6.*unaffected
  • 6.12.109 to ≤ 6.12.*unaffected
  • 6.18.50 to ≤ 6.18.*unaffected
  • 7.2.4 to ≤ 7.2.*unaffected
  • 7.3 to ≤ *unaffected

References