From: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Subject: kasan, mm: fix resetting page_alloc tags for HW_TAGS A previous commit added resetting KASAN page tags to kernel_init_free_pages() to avoid false-positives due to accesses to metadata with the hardware tag-based mode. That commit did reset page tags before the metadata access, but didn't restore them after. As the result, KASAN fails to detect bad accesses to page_alloc allocations on some configurations. Fix this by recovering the tag after the metadata access. Link: https://lkml.kernel.org/r/02b5bcd692e912c27d484030f666b350ad7e4ae4.1611074450.git.andreyknvl@xxxxxxxxxx Fixes: aa1ef4d7b3f6 ("kasan, mm: reset tags when accessing metadata") Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Marco Elver <elver@xxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Will Deacon <will.deacon@xxxxxxx> Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Cc: Peter Collingbourne <pcc@xxxxxxxxxx> Cc: Evgenii Stepanov <eugenis@xxxxxxxxxx> Cc: Branislav Rankov <Branislav.Rankov@xxxxxxx> Cc: Kevin Brodsky <kevin.brodsky@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 2 ++ 1 file changed, 2 insertions(+) --- a/mm/page_alloc.c~kasan-mm-fix-resetting-page_alloc-tags-for-hw_tags +++ a/mm/page_alloc.c @@ -1207,8 +1207,10 @@ static void kernel_init_free_pages(struc /* s390's use of memset() could override KASAN redzones. */ kasan_disable_current(); for (i = 0; i < numpages; i++) { + u8 tag = page_kasan_tag(page + i); page_kasan_tag_reset(page + i); clear_highpage(page + i); + page_kasan_tag_set(page + i, tag); } kasan_enable_current(); } _
