Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: Qian Cai <cai@lca.pw>
To: akpm@linux-foundation.org
Cc: aryabinin@virtuozzo.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, Qian Cai <cai@lca.pw>
Subject: [PATCH v2] page_poison: play nicely with KASAN
Date: Mon, 14 Jan 2019 18:34:05 -0500
Message-ID: <20190114233405.67843-1-cai@lca.pw> (raw)
In-Reply-To: <2e46c139-70d3-dc86-28c9-a9f263651b57@virtuozzo.com>

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@lca.pw>
---

v2: use kasan_disable/enable_current() instead.

 mm/page_alloc.c  | 2 +-
 mm/page_poison.c | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d295c9bc01a8..906250a9b89c 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);
 }
 
-- 
2.17.2 (Apple Git-113)

  reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-07 22:36 [PATCH] page_poison: plays " Qian Cai
2019-01-11 18:45 ` Andrey Ryabinin
2019-01-14 23:34   ` Qian Cai [this message]
2019-01-15 17:25     ` [PATCH v2] page_poison: play " Andrey Ryabinin

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190114233405.67843-1-cai@lca.pw \
    --to=cai@lca.pw \
    --cc=akpm@linux-foundation.org \
    --cc=aryabinin@virtuozzo.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org linux-mm@archiver.kernel.org
	public-inbox-index linux-mm


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/ public-inbox