In the Linux kernel, the following vulnerability has been resolved:
wifi: brcmfmac: fix use-after-free when rescheduling brcmf_btcoex_info work
The brcmf_btcoex_detach() only shuts down the btcoex timer, if the
flag timer_on is false. However, the brcmf_btcoex_timerfunc(), which
runs as timer handler, sets timer_on to false. This creates critical
race conditions:
1.If brcmf_btcoex_detach() is called while brcmf_btcoex_timerfunc()
is executing, it may observe timer_on as false and skip the call to
timer_shutdown_sync().
2.The brcmf_btcoex_timerfunc() may then reschedule the brcmf_btcoex_info
worker after the cancel_work_sync() has been executed, resulting in
use-after-free bugs.
The use-after-free bugs occur in two distinct scenarios, depending on
the timing of when the brcmf_btcoex_info struct is freed relative to
the execution of its worker thread.
Scenario 1: Freed before the worker is scheduled
The brcmf_btcoex_info is deallocated before the worker is scheduled.
A race condition can occur when schedule_work(&bt_local->work) is
called after the target memory has been freed. The sequence of events
is detailed below:
CPU0 | CPU1
brcmf_btcoex_detach | brcmf_btcoex_timerfunc
| bt_local->timer_on = false;
if (cfg->btcoex->timer_on) |
... |
cancel_work_sync(); |
... |
kfree(cfg->btcoex); // FREE |
| schedule_work(&bt_local->work); // USE
Scenario 2: Freed after the worker is scheduled
The brcmf_btcoex_info is freed after the worker has been scheduled
but before or during its execution. In this case, statements within
the brcmf_btcoex_handler() — such as the container_of macro and
subsequent dereferences of the brcmf_btcoex_info object will cause
a use-after-free access. The following timeline illustrates this
scenario:
CPU0 | CPU1
brcmf_btcoex_detach | brcmf_btcoex_timerfunc
| bt_local->timer_on = false;
if (cfg->btcoex->timer_on) |
... |
cancel_work_sync(); |
... | schedule_work(); // Reschedule
|
kfree(cfg->btcoex); // FREE | brcmf_btcoex_handler() // Worker
/* | btci = container_of(....); // USE
The kfree() above could | ...
also occur at any point | btci-> // USE
during the worker's execution|
*/ |
To resolve the race conditions, drop the conditional check and call
timer_shutdown_sync() directly. It can deactivate the timer reliably,
regardless of its current state. Once stopped, the timer_on state is
then set to false.
References
Configurations
Configuration 1 (hide)
|
History
12 Dec 2025, 20:09
| Type | Values Removed | Values Added |
|---|---|---|
| References | () https://git.kernel.org/stable/c/2f6fbc8e04ca1d1d5c560be694199f847229c625 - Patch | |
| References | () https://git.kernel.org/stable/c/3e789f8475f6c857c88de5c5bf4b24b11a477dd7 - Patch | |
| References | () https://git.kernel.org/stable/c/9cb83d4be0b9b697eae93d321e0da999f9cdfcfc - Patch | |
| References | () https://git.kernel.org/stable/c/f1150153c4e5940fe49ab51136343c5b4fe49d63 - Patch | |
| CPE | cpe:2.3:o:linux:linux_kernel:6.17:rc4:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:* |
|
| CWE | CWE-416 | |
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 7.8 |
| First Time |
Linux
Linux linux Kernel |
19 Sep 2025, 16:15
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2025-09-19 16:15
Updated : 2025-12-12 20:09
NVD link : CVE-2025-39863
Mitre link : CVE-2025-39863
CVE.ORG link : CVE-2025-39863
JSON object : View
Products Affected
linux
- linux_kernel
CWE
CWE-416
Use After Free