On 9/18/25 7:52 PM, Gui-Dong Han wrote:

When do_task() exhausts its iteration budget (!ret), it sets the state to TASK_STATE_IDLE to reschedule, without a secondary check on the current task->state. This can overwrite the TASK_STATE_DRAINING state set by a concurrent call to rxe_cleanup_task() or rxe_disable_task().

While state changes are protected by a spinlock, both rxe_cleanup_task() and rxe_disable_task() release the lock while waiting for the task to finish draining in the while(!is_done(task)) loop. The race occurs if do_task() hits its iteration limit and acquires the lock in this window. The cleanup logic may then proceed while the task incorrectly reschedules itself, leading to a potential use-after-free.

This bug was introduced during the migration from tasklets to workqueues, where the special handling for the draining case was lost.

Fix this by restoring the original pre-migration behavior. If the state is TASK_STATE_DRAINING when iterations are exhausted, set cont to 1 to force a new loop iteration. This allows the task to finish its work, so that a subsequent iteration can reach the switch statement and correctly transition the state to TASK_STATE_DRAINED, stopping the task as intended.

Fixes: 9b4b7c1f9f54 ("RDMA/rxe: Add workqueue support for rxe tasks") Cc: stable@vger.kernel.org Reviewed-by: Zhu Yanjun yanjun.zhu@linux.dev

Thanks a lot. I am fine with this.

Yanjun.Zhu

Signed-off-by: Gui-Dong Han hanguidong02@gmail.com

v2:

• Rewrite commit message for clarity. Thanks to Zhu Yanjun for the review.

---

drivers/infiniband/sw/rxe/rxe_task.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_task.c b/drivers/infiniband/sw/rxe/rxe_task.c index 6f8f353e9583..f522820b950c 100644 --- a/drivers/infiniband/sw/rxe/rxe_task.c +++ b/drivers/infiniband/sw/rxe/rxe_task.c @@ -132,8 +132,12 @@ static void do_task(struct rxe_task *task) * yield the cpu and reschedule the task */ if (!ret) {

• 	task->state = TASK_STATE_IDLE;
  

• 	resched = 1;
  

• 	if (task->state != TASK_STATE_DRAINING) {
  

• 		task->state = TASK_STATE_IDLE;
  

• 		resched = 1;
  

• 	} else {
  

• 		cont = 1;
  

• 	}
  goto exit;
  

  }