Commit a38a6471 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

unwind: Fix unwind_deferred_request() vs NMI 



task_work_add(RWA_RESUME) isn't NMI-safe, use TWA_NMI_CURRENT when
used from NMI context.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Link: https://patch.msgid.link/20250924080119.005422353@infradead.org
parent ae577ea0

kernel/unwind/deferred.c

+7 −3
Original line number Diff line number Diff line
@@ -231,6 +231,7 @@ void unwind_deferred_task_exit(struct task_struct *task) 
int unwind_deferred_request(struct unwind_work *work, u64 *cookie)

{

	struct unwind_task_info *info = &current->unwind_info;

	int twa_mode = TWA_RESUME;

	unsigned long old, bits;

	unsigned long bit;

	int ret;
@@ -246,8 +247,11 @@ int unwind_deferred_request(struct unwind_work *work, u64 *cookie) 
	 * Trigger a warning to make it obvious that an architecture

	 * is using this in NMI when it should not be.

	 */

	if (WARN_ON_ONCE(!CAN_USE_IN_NMI && in_nmi()))

	if (in_nmi()) {

		if (WARN_ON_ONCE(!CAN_USE_IN_NMI))

			return -EINVAL;

		twa_mode = TWA_NMI_CURRENT;

	}



	/* Do not allow cancelled works to request again */

	bit = READ_ONCE(work->bit);
@@ -285,7 +289,7 @@ int unwind_deferred_request(struct unwind_work *work, u64 *cookie) 
	}



	/* The work has been claimed, now schedule it. */

	ret = task_work_add(current, &info->work, TWA_RESUME);

	ret = task_work_add(current, &info->work, twa_mode);



	if (WARN_ON_ONCE(ret))

		WRITE_ONCE(info->unwind_mask, 0);