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CVE PROGRAM SOURCE RECORD7.8 High

CVE-2026-72123

can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF Commit f1b4e32aca08 ("can: bcm: use call_rcu() instead of costly synchronize_rcu()") replaced synchronize_rcu() in bcm_delete_rx_op() with call_rcu() and introduced the RX_NO_AUTOTIMER flag. However, this flag check was omitted for thrtimer in the packet rx fast-path. During BCM RX operation teardown, a concurrent RCU reader (bcm_rx_handler) can race and re-arm thrtimer via bcm_rx_update_and_send() after call_rcu() has been scheduled. Once the RCU grace period elapses, bcm_op is freed. The subsequently firing thrtimer then dereferences the deallocated op, causing a UAF. Adding flag checks to the rx fast-path (bcm_rx_update_and_send) does not fully close the TOCTOU race and introduces latency for every CAN frame. Conversely, calling hrtimer_cancel() directly inside the RCU callback (softirq context) is fatal as hrtimer_cancel() can sleep, triggering a "scheduling while atomic" panic. Resolve this by deferring the timer cancellation and memory free to a dedicated unbound workqueue (bcm_wq). The RCU callback now queues a work item to bcm_wq, which safely cancels both timers and deallocates memory in sleepable process context. A dedicated workqueue is used to prevent system-wide WQ saturation and is cleanly flushed/destroyed on module unload to avoid rmmod page faults. Since the deferred work can now outlive the calling context by an unbounded amount, also take a reference on op->sk when it is assigned and drop it only once the deferred work has cancelled both timers, so a socket can no longer be freed out from under a still-armed timer whose callback (bcm_send_to_user()) dereferences op->sk.

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

  • 85cd41070df992d3c0dfd828866fdd243d3b774a to < de5fce46637de05bef56ec08528127676eb6fc9baffected
  • f34f2a18e47b73e48f90a757e1f4aaa8c7d665a1 to < 036a8c320ca11bc912e8027adcfad14b326f067eaffected
  • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 to < 3cf4fd5316f449811d8baf1bc6978ef5a7b743a9affected
  • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 to < 4177762f70646ac48a2af382e45a795cbd295198affected
  • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 to < 6fd08e8d826c3aa4cc7021f5f9cdbb7fa7441d3faffected
  • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 to < cd830e0bc25ee2d38cbfbdbb3cd77c5f53b2b6d5affected
  • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 to < ce2d4b121fb7545e1ed588e860c8e5fd5ad45224affected
  • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 to < 68973f9db76144825e4f35dfdc80fb8279eb2d57affected
  • fbac09a3b8890003c0c55294c00709f3ae5501bbaffected
  • 5b48f5711f1c630841ab78dcc061de902f0e37bfaffected
  • edb4baffb9483141a50fb7f7146cfe4a4c0c2db8affected
  • 5.10.130 to < 5.10.265affected
  • 5.15.54 to < 5.15.216affected
  • 4.19.252 to < 4.20affected
  • 5.4.205 to < 5.5affected
  • 5.18.11 to < 5.19affected

Linux Linux

Default version status: affected

  • 5.19affected
  • 0 to < 5.19unaffected
  • 5.10.265 to ≤ 5.10.*unaffected
  • 5.15.216 to ≤ 5.15.*unaffected
  • 6.1.178 to ≤ 6.1.*unaffected
  • 6.6.145 to ≤ 6.6.*unaffected
  • 6.12.97 to ≤ 6.12.*unaffected
  • 6.18.40 to ≤ 6.18.*unaffected
  • 7.1.5 to ≤ 7.1.*unaffected
  • 7.2 to ≤ *unaffected

References