Description (CNA)
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 (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 85cd41070df992d3c0dfd828866fdd243d3b774a before de5fce46637de05bef56ec08528127676eb6fc9b; affected f34f2a18e47b73e48f90a757e1f4aaa8c7d665a1 before 036a8c320ca11bc912e8027adcfad14b326f067e; affected f1b4e32aca0811aa011c76e5d6cf2fa19224b386 before 3cf4fd5316f449811d8baf1bc6978ef5a7b743a9; affected f1b4e32aca0811aa011c76e5d6cf2fa19224b386 before 4177762f70646ac48a2af382e45a795cbd295198; affected f1b4e32aca0811aa011c76e5d6cf2fa19224b386 before 6fd08e8d826c3aa4cc7021f5f9cdbb7fa7441d3f; affected f1b4e32aca0811aa011c76e5d6cf2fa19224b386 before cd830e0bc25ee2d38cbfbdbb3cd77c5f53b2b6d5; affected f1b4e32aca0811aa011c76e5d6cf2fa19224b386 before ce2d4b121fb7545e1ed588e860c8e5fd5ad45224; affected f1b4e32aca0811aa011c76e5d6cf2fa19224b386 before 68973f9db76144825e4f35dfdc80fb8279eb2d57; affected fbac09a3b8890003c0c55294c00709f3ae5501bb; affected 5b48f5711f1c630841ab78dcc061de902f0e37bf; affected edb4baffb9483141a50fb7f7146cfe4a4c0c2db8; affected 5.10.130 before 5.10.265; affected 5.15.54 before 5.15.216; affected 4.19.252 before 4.20; affected 5.4.205 before 5.5; affected 5.18.11 before 5.19 |
| Linux / Linux | affected 5.19; unaffected 0 before 5.19; unaffected 5.10.265 through 5.10.*; unaffected 5.15.216 through 5.15.*; unaffected 6.1.178 through 6.1.*; unaffected 6.6.145 through 6.6.*; unaffected 6.12.97 through 6.12.*; unaffected 6.18.40 through 6.18.*; unaffected 7.1.5 through 7.1.*; unaffected 7.2 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/de5fce46637de05bef56ec08528127676eb6fc9b
- https://git.kernel.org/stable/c/036a8c320ca11bc912e8027adcfad14b326f067e
- https://git.kernel.org/stable/c/3cf4fd5316f449811d8baf1bc6978ef5a7b743a9
- https://git.kernel.org/stable/c/4177762f70646ac48a2af382e45a795cbd295198
- https://git.kernel.org/stable/c/6fd08e8d826c3aa4cc7021f5f9cdbb7fa7441d3f
- https://git.kernel.org/stable/c/cd830e0bc25ee2d38cbfbdbb3cd77c5f53b2b6d5
- https://git.kernel.org/stable/c/ce2d4b121fb7545e1ed588e860c8e5fd5ad45224
- https://git.kernel.org/stable/c/68973f9db76144825e4f35dfdc80fb8279eb2d57
ADP enrichment
No English description supplied.
No references supplied.