michael/linux
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

mm: kmsan: fix poisoning of high-order non-compound pages

Browse Source 
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>
This commit is contained in:
Ryan Roberts
2026-01-04 13:43:47 +00:00
committed by Andrew Morton
parent fb39444732
commit 4795d205d7
1 changed files with 1 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
mm/kmsan/shadow.c
View File

@@ -207,7 +207,7 @@ void kmsan_free_page(struct page *page, unsigned int order)
if (!kmsan_enabled || kmsan_in_runtime())
return;
kmsan_enter_runtime();
kmsan_internal_poison_memory(page_address(page), page_size(page),
kmsan_internal_poison_memory(page_address(page), PAGE_SIZE << order,
GFP_KERNEL & ~(__GFP_RECLAIM),
KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
kmsan_leave_runtime();