coredump: hold RCU while releasing parked threads

In the Linux kernel, the following vulnerability has been resolved: coredump: hold RCU while releasing parked threads coredump_finish() releases the parked threads by clearing ->task in their core_thread entry and calling wake_up_process() on each of them. It does that without holding a reference on the task and without being inside rcu. But calling wake_up_process(task) without rcu here isn't safe. A parked thread doesn't need that wakeup to leave. A spurious wakeup or a preemption after the store is enough for the task to go away. So if the coredump client is preempted between the store and wake_up_process() the thread can exit and be freed in the meantime and try_to_wake_up() takes pi_lock in freed memory. Hold rcu across the loop.

Source published

2 Nov 2026 16:06:31 UTC

Source modified

2 Nov 2026 16:06:31 UTC

Observed here

2 Nov 2026 17:57:17 UTC

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CVSS 3.1 · 7.0 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H