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events: Reuse value read using READ_ONCE instead of re-reading it 

commit b89a05b21f46150ac10a962aa50109250b56b03b upstream.

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: 375637bc52 ("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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Baptiste Lepers 2021-09-06 11:53:10 +10:00 committed by Greg Kroah-Hartman
parent cd78d9c996
commit 172749c879
1 changed files with 1 additions and 1 deletions
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2
kernel/events/core.c
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@ -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;