linux-kernel - Re: f2fs: BUG_ON() is triggered when mount valid f2fs filesystem

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Message-id: <1397802904.4283.1.camel@kjgkr>
Date:	Fri, 18 Apr 2014 15:35:04 +0900
From:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
To:	Alexey Khoroshilov <khoroshilov@...ras.ru>
Cc:	Andrey Tsyvarev <tsyvarev@...ras.ru>,
	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: f2fs: BUG_ON() is triggered when mount valid f2fs filesystem

Thank you for the explanation.
The following patch will resolve the issue.
Thanks,

>From 2048e7458c982f4297da9d3366ab29224ae2e8b0 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk.kim@...sung.com>
Date: Fri, 18 Apr 2014 15:21:04 +0900
Subject: [PATCH] f2fs: avoid BUG_ON when mouting corrupted image having
 garbage blocks

If the disk has some garbage blocks, F2FS is able to face with BUG_ON
when
recovering direct node blocks.
This patch detects the error case and avoids that prior to reaching
BUG_ON.

Alexey Khoroshilov addressed the potential security issues as follows.
"An ability to trigger a BUG_ON assert by mounting a crafted image is
usually considered as a local denial of service [1-3]. As far as I
understand, the reason is that some kernel data may become inconsistent
that can lead to further problems.

[1] http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-3353
[2] http://www.openwall.com/lists/oss-security/2011/06/24/4
[3] http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-2928
etc."

Reported-by: Andrey Tsyvarev <tsyvarev@...ras.ru>
Cc: Alexey Khoroshilov <khoroshilov@...ras.ru>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@...sung.com>
---
 fs/f2fs/node.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 6ebdba1..64755f4 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1609,6 +1609,11 @@ int recover_inode_page(struct f2fs_sb_info *sbi,
struct page *page)
 	struct node_info old_ni, new_ni;
 	struct page *ipage;
 
+	get_node_info(sbi, ino, &old_ni);
+
+	if (unlikely(old_ni.blk_addr != NULL_ADDR))
+		return -EINVAL;
+
 	ipage = grab_cache_page(NODE_MAPPING(sbi), ino);
 	if (!ipage)
 		return -ENOMEM;
@@ -1616,7 +1621,6 @@ int recover_inode_page(struct f2fs_sb_info *sbi,
struct page *page)
 	/* Should not use this inode  from free nid list */
 	remove_free_nid(NM_I(sbi), ino);
 
-	get_node_info(sbi, ino, &old_ni);
 	SetPageUptodate(ipage);
 	fill_node_footer(ipage, ino, ino, 0, true);
 
-- 
1.8.4.474.g128a96c




-- 
Jaegeuk Kim
Samsung

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