From: Adrian Hunter Date: Mon, 24 Jun 2024 20:11:00 +0000 (+0300) Subject: perf: Fix default aux_watermark calculation X-Git-Tag: v6.11-rc1~168^2~30 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=43deb76b19663a96ec2189d8f4eb9a9dc2d7623f;p=thirdparty%2Flinux.git 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 Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20240624201101.60186-7-adrian.hunter@intel.com --- diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 4013408ce0123..485cf0a66631b 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