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linux/mm/kmsan
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Ryan Roberts d1beb4dd8b mm: kmsan: fix poisoning of high-order non-compound pages 
[ Upstream commit 4795d205d7 ]

kmsan_free_page() is called by the page allocator's free_pages_prepare()
during page freeing.  Its job is to poison all the memory covered by the
page.  It can be called with an order-0 page, a compound high-order page
or a non-compound high-order page.  But page_size() only works for order-0
and compound pages.  For a non-compound high-order page it will
incorrectly return PAGE_SIZE.

The implication is that the tail pages of a high-order non-compound page
do not get poisoned at free, so any invalid access while they are free
could go unnoticed.  It looks like the pages will be poisoned again at
allocation time, so that would bookend the window.

Fix this by using the order parameter to calculate the size.

Link: https://lkml.kernel.org/r/20260104134348.3544298-1-ryan.roberts@arm.com
Fixes: b073d7f8ae ("mm: kmsan: maintain KMSAN metadata for page operations")
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Tested-by: Alexander Potapenko <glider@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[ Adjust context ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-01-23 11:18:51 +01:00
..
core.c kmsan: fix out-of-bounds access to shadow memory 2025-10-02 13:44:14 +02:00
hooks.c dma: kmsan: export kmsan_handle_dma() for modules 2025-03-13 13:01:58 +01:00
init.c kmsan: accept ranges starting with 0 on s390 2024-07-03 19:30:23 -07:00
instrumentation.c kmsan: do not pass NULL pointers as 0 2024-07-03 19:30:26 -07:00
kmsan.h kmsan: add missing __user tags 2024-07-03 19:30:26 -07:00
kmsan_test.c kmsan: fix out-of-bounds access to shadow memory 2025-10-02 13:44:14 +02:00
Makefile kmsan: disable ftrace in kmsan core code 2023-02-20 12:46:16 -08:00
report.c kmsan: add missing __user tags 2024-07-03 19:30:26 -07:00
shadow.c mm: kmsan: fix poisoning of high-order non-compound pages 2026-01-23 11:18:51 +01:00