The following commit has been merged into the perf/core branch of tip:
Commit-ID: 43deb76b19663a96ec2189d8f4eb9a9dc2d7623f
Gitweb: https://git.kernel.org/tip/43deb76b19663a96ec2189d8f4eb9a9dc2d7623f
Author: Adrian Hunter <adrian.hunter@xxxxxxxxx>
AuthorDate: Mon, 24 Jun 2024 23:11:00 +03:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Thu, 04 Jul 2024 16:00:23 +02:00
perf: Fix default aux_watermark calculation
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
---
kernel/events/ring_buffer.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 4013408..485cf0a 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -688,7 +688,9 @@ 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
|