linux-kernel - Re: [PATCH 1/1] nilfs2: fix potential memory overrun on inode

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Message-Id: <20150221.101328.1613471465739082397.konishi.ryusuke@lab.ntt.co.jp>
Date:	Sat, 21 Feb 2015 10:13:28 +0900 (JST)
From:	Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-nilfs@...r.kernel.org
Subject: Re: [PATCH 1/1] nilfs2: fix potential memory overrun on inode

On Sat, 21 Feb 2015 09:22:08 +0900 (JST), Ryusuke Konishi wrote:
> On Fri, 20 Feb 2015 13:58:42 -0800, Andrew Morton wrote:
>> On Fri, 20 Feb 2015 22:46:35 +0900 Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp> wrote:
>> 
>>> Each inode of nilfs2 stores a root node of a b-tree, and it turned out
>>> to have a memory overrun issue:
>>> 
>>> Each b-tree node of nilfs2 stores a set of key-value pairs and the
>>> number of them (in "bn_nchildren" member of nilfs_btree_node struct),
>>> as well as a few other "bn_*" members.
>>> 
>>> Since the value of "bn_nchildren" is used for operations on the
>>> key-values within the b-tree node, it can cause memory access overrun
>>> if a large number is incorrectly set to "bn_nchildren".
>>> 
>>> For instance, nilfs_btree_node_lookup() function determines the range
>>> of binary search with it, and too large "bn_nchildren" leads
>>> nilfs_btree_node_get_key() in that function to overrun.
>>> 
>>> As for intermediate b-tree nodes, this is prevented by a sanity check
>>> performed when each node is read from a drive, however, no sanity
>>> check has been done for root nodes stored in inodes.
>>> 
>>> This patch fixes the issue by adding missing sanity check against
>>> b-tree root nodes so that it's called when on-memory inodes are read
>>> from ifile, inode metadata file.
>> 
>> How would one trigger this overrun?  Mount an fs with a deliberately
>> corrupted/inconsistent fs image?
> 
> Yes, this can be triggered by mounting an fs with a corrupted image
> deliberately or by chance.
> 
>> Memory overrun sounds nasty so I'm thinking we add cc:stable to this
>> one.  OK?
> 
> Agreed.

Could you apply the following amendment ?

I've got a warning from 0day kernel testing backend:

    fs/nilfs2/btree.c: In function 'nilfs_btree_root_broken':
>> fs/nilfs2/btree.c:394:3: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'ino_t' [-Wformat=]
       pr_crit("NILFS: bad btree root (inode number=%lu): level = %d, 
flags = 0x%x, nchildren = %d\n",
       ^

This is output for s390 arch since ino_t doesn't mean "unsigned long"
in s390.

Thanks,
Ryusuke Konishi
--
diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index c645d7c..ecdbae1 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -378,7 +378,7 @@ static int nilfs_btree_node_broken(const struct nilfs_btree_node *node,
  * Return Value: If node is broken, 1 is returned. Otherwise, 0 is returned.
  */
 static int nilfs_btree_root_broken(const struct nilfs_btree_node *node,
-				   ino_t ino)
+				   unsigned long ino)
 {
 	int level, flags, nchildren;
 	int ret = 0;
-- 
1.8.3.1

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