5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Adrian Hunter adrian.hunter@intel.com
[ 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@intel.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lore.kernel.org/r/20240624201101.60186-7-adrian.hunter@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 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