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
mismatch.

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3beeb8d722f37d8c949e9923360fb77c140a6a13..1887852fb934fed89da802eaecc8dc445f0a4c43 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7671,6 +7671,11 @@ unsigned long free_reserved_area(void *start, void *end, int poison, const char
                 * 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);