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authorQian Cai <cai@lca.pw>2019-03-05 15:41:24 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-03-05 21:07:13 -0800
commit4117992df66a26fa33908b4969e04801534baab1 (patch)
tree2001a4fdda8cb39faa3aeef8857e8f9d89bd5973
parent7771bdbbfd3d6f204631b6fd9e1bbc30cd15918e (diff)
downloadlinux-4117992df66a26fa33908b4969e04801534baab1.tar.bz2
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@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: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/page_alloc.c2
-rw-r--r--mm/page_poison.c4
2 files changed, 5 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0b9f577b1a2a..10d0f2ed9f69 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1945,8 +1945,8 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
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);
}
diff --git a/mm/page_poison.c b/mm/page_poison.c
index f0c15e9017c0..21d4f97cb49b 100644
--- a/mm/page_poison.c
+++ b/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 *page)
{
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);
}