This is a note to let you know that I've just added the patch titled events: Reuse value read using READ_ONCE instead of re-reading it to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: events-reuse-value-read-using-read_once-instead-of-r.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 83670a6583b6a82b95922767c71ef5f995d2c1d9 Author: Baptiste Lepers <baptiste.lepers@xxxxxxxxx> Date: Mon Sep 6 11:53:10 2021 +1000 events: Reuse value read using READ_ONCE instead of re-reading it [ Upstream commit b89a05b21f46150ac10a962aa50109250b56b03b ] In perf_event_addr_filters_apply, the task associated with the event (event->ctx->task) is read using READ_ONCE at the beginning of the function, checked, and then re-read from event->ctx->task, voiding all guarantees of the checks. Reuse the value that was read by READ_ONCE to ensure the consistency of the task struct throughout the function. Fixes: 375637bc52495 ("perf/core: Introduce address range filtering") Signed-off-by: Baptiste Lepers <baptiste.lepers@xxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20210906015310.12802-1-baptiste.lepers@xxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/kernel/events/core.c b/kernel/events/core.c index 2f848123cdae..1993a741d2dc 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9259,7 +9259,7 @@ static void perf_event_addr_filters_apply(struct perf_event *event) return; if (ifh->nr_file_filters) { - mm = get_task_mm(event->ctx->task); + mm = get_task_mm(task); if (!mm) goto restart;