diff mbox series

[43/78] kasan, mm: untag page address in free_reserved_area

Message ID 20201218220346.OSOCAeHhM%akpm@linux-foundation.org (mailing list archive)
State New, archived
Headers show
Series [01/78] mm/memcg: bail early from swap accounting if memcg disabled | expand

Commit Message

Andrew Morton Dec. 18, 2020, 10:03 p.m. UTC
From: Vincenzo Frascino <vincenzo.frascino@arm.com>
Subject: kasan, mm: untag page address in free_reserved_area

free_reserved_area() memsets the pages belonging to a given memory area. 
As that memory hasn't been allocated via page_alloc, the KASAN tags that
those pages have are 0x00.  As the result the memset might result in a tag

Untag the address to avoid spurious faults.

Link: https://lkml.kernel.org/r/ebef6425f4468d063e2f09c1b62ccbb2236b71d3.1606161801.git.andreyknvl@google.com
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Marco Elver <elver@google.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

 mm/page_alloc.c |    5 +++++
 1 file changed, 5 insertions(+)
diff mbox series


--- a/mm/page_alloc.c~kasan-mm-untag-page-address-in-free_reserved_area
+++ a/mm/page_alloc.c
@@ -7671,6 +7671,11 @@  unsigned long free_reserved_area(void *s
 		 * alias for the memset().
 		direct_map_addr = page_address(page);
+		/*
+		 * Perform a kasan-unchecked memset() since this memory
+		 * has not been initialized.
+		 */
+		direct_map_addr = kasan_reset_tag(direct_map_addr);
 		if ((unsigned int)poison <= 0xFF)
 			memset(direct_map_addr, poison, PAGE_SIZE);