The patch titled
Subject: page_poison: play nicely with KASAN
has been added to the -mm tree. Its filename is
page_poison-play-nicely-with-kasan.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/page_poison-play-nicely-with-kasan.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/page_poison-play-nicely-with-kasan.patch
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------------------------------------------------------
From: Qian Cai <cai@xxxxxx>
Subject: page_poison: play nicely with KASAN
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@xxxxxx
Signed-off-by: Qian Cai <cai@xxxxxx>
Acked-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 2 +-
mm/page_poison.c | 4 ++++
2 files changed, 5 insertions(+), 1 deletion(-)
--- a/mm/page_alloc.c~page_poison-play-nicely-with-kasan
+++ a/mm/page_alloc.c
@@ -1945,8 +1945,8 @@ inline void post_alloc_hook(struct page
arch_alloc_page(page, order);
kernel_map_pages(page, 1 << order, 1);
- kernel_poison_pages(page, 1 << order, 1);
kasan_alloc_pages(page, order);
+ kernel_poison_pages(page, 1 << order, 1);
set_page_owner(page, order, gfp_flags);
}
--- a/mm/page_poison.c~page_poison-play-nicely-with-kasan
+++ a/mm/page_poison.c
@@ -6,6 +6,7 @@
#include <linux/page_ext.h>
#include <linux/poison.h>
#include <linux/ratelimit.h>
+#include <linux/kasan.h>
static bool want_page_poisoning __read_mostly;
@@ -40,7 +41,10 @@ static void poison_page(struct page *pag
{
void *addr = kmap_atomic(page);
+ /* KASAN still think the page is in-use, so skip it. */
+ kasan_disable_current();
memset(addr, PAGE_POISON, PAGE_SIZE);
+ kasan_enable_current();
kunmap_atomic(addr);
}
_
Patches currently in -mm which might be from cai@xxxxxx are
mm-page_owner-fix-for-deferred-struct-page-init.patch
x86_64-increase-stack-size-for-kasan_extra.patch
mm-hotplug-invalid-pfns-from-pfn_to_online_page.patch
page_poison-play-nicely-with-kasan.patch
slab-kmemleak-no-scan-alien-caches.patch
page_poison-plays-nicely-with-kasan.patch
signal-allow-the-null-signal-in-rt_sigqueueinfo.patch
