page_poison: play nicely with KASAN

mainline inclusion
from mainline-5.0
commit 4117992d
category: bugfix
bugzilla: 11620
CVE: NA

------------------------------------------------

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.

Link: http://lkml.kernel.org/r/20190114233405.67843-1-cai@lca.pw


Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Reviewed-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>