CVE-2026-23400

Summary

In the Linux kernel, the following vulnerability has been resolved:

rust_binder: call set_notification_done() without proc lock

Consider the following sequence of events on a death listener:

1. The remote process dies and sends a BR_DEAD_BINDER message.
2. The local process invokes the BC_CLEAR_DEATH_NOTIFICATION command.
3. The local process then invokes the BC_DEAD_BINDER_DONE. Then, the kernel will reply to the BC_DEAD_BINDER_DONE command with a BR_CLEAR_DEATH_NOTIFICATION_DONE reply using push_work_if_looper().

However, this can result in a deadlock if the current thread is not a looper. This is because dead_binder_done() still holds the proc lock during set_notification_done(), which called push_work_if_looper(). Normally, push_work_if_looper() takes the thread lock, which is fine to take under the proc lock. But if the current thread is not a looper, then it falls back to delivering the reply to the process work queue, which involves taking the proc lock. Since the proc lock is already held, this is a deadlock.

Fix this by releasing the proc lock during set_notification_done(). It was not intentional that it was held during that function to begin with.

I don't think this ever happens in Android because BC_DEAD_BINDER_DONE is only invoked in response to BR_DEAD_BINDER messages, and the kernel always delivers BR_DEAD_BINDER to a looper. So there's no scenario where Android userspace will call BC_DEAD_BINDER_DONE on a non-looper thread.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/dd109e3442817bc03ad1f3ffd541092f8c428141
• https://git.kernel.org/stable/c/3be72099067d2cd4a0e089696f19780f75b2b88a
• https://git.kernel.org/stable/c/2e303f0febb65a434040774b793ba8356698802b

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