This is a note to let you know that I've just added the patch titled
perf: Fix default aux_watermark calculation
to the 5.15-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:
perf-fix-default-aux_watermark-calculation.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 7ff322bcbc9c69cd542f1b2dcfa222d941781bc9
Author: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Date: Mon Jun 24 23:11:00 2024 +0300
perf: Fix default aux_watermark calculation
[ Upstream commit 43deb76b19663a96ec2189d8f4eb9a9dc2d7623f ]
The default aux_watermark is half the AUX area buffer size. In general,
on a 64-bit architecture, the AUX area buffer size could be a bigger than
fits in a 32-bit type, but the calculation does not allow for that
possibility.
However the aux_watermark value is recorded in a u32, so should not be
more than U32_MAX either.
Fix by doing the calculation in a correctly sized type, and limiting the
result to U32_MAX.
Fixes: d68e6799a5c8 ("perf: Cap allocation order at aux_watermark")
Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240624201101.60186-7-adrian.hunter@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 45965f13757e4..f3a3c294ff2b3 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -683,7 +683,9 @@ int rb_alloc_aux(struct perf_buffer *rb, struct perf_event *event,
* max_order, to aid PMU drivers in double buffering.
*/
if (!watermark)
- watermark = nr_pages << (PAGE_SHIFT - 1);
+ watermark = min_t(unsigned long,
+ U32_MAX,
+ (unsigned long)nr_pages << (PAGE_SHIFT - 1));
/*
* Use aux_watermark as the basis for chunking to
