events: Reuse value read using READ_ONCE instead of re-reading it
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@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210906015310.12802-1-baptiste.lepers@gmail.com
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 744e872..0c000cb 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10193,7 +10193,7 @@
return;
if (ifh->nr_file_filters) {
- mm = get_task_mm(event->ctx->task);
+ mm = get_task_mm(task);
if (!mm)
goto restart;
