On 1/15/19 2:34 AM, Qian Cai wrote: > KASAN does not play well with the page poisoning > (CONFIG_PAGE_POISONING). It triggers false positives in the allocation > path, > > BUG: KASAN: use-after-free in memchr_inv+0x2ea/0x330 > Read of size 8 at addr ffff88881f800000 by task swapper/0 > CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc1+ #54 > Call Trace: > dump_stack+0xe0/0x19a > print_address_description.cold.2+0x9/0x28b > kasan_report.cold.3+0x7a/0xb5 > __asan_report_load8_noabort+0x19/0x20 > memchr_inv+0x2ea/0x330 > kernel_poison_pages+0x103/0x3d5 > get_page_from_freelist+0x15e7/0x4d90 > > because KASAN has not yet unpoisoned the shadow page for allocation > before it checks memchr_inv() but only found a stale poison pattern. > > Also, false positives in free path, > > BUG: KASAN: slab-out-of-bounds in kernel_poison_pages+0x29e/0x3d5 > Write of size 4096 at addr ffff8888112cc000 by task swapper/0/1 > CPU: 5 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc1+ #55 > Call Trace: > dump_stack+0xe0/0x19a > print_address_description.cold.2+0x9/0x28b > kasan_report.cold.3+0x7a/0xb5 > check_memory_region+0x22d/0x250 > memset+0x28/0x40 > kernel_poison_pages+0x29e/0x3d5 > __free_pages_ok+0x75f/0x13e0 > > due to KASAN adds poisoned redzones around slab objects, but the page > poisoning needs to poison the whole page. > > Signed-off-by: Qian Cai <cai@xxxxxx> > --- > Acked-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
