Re: [Patch] BUG in fs/jfs/jfs_xtree.c

[Dave Kleikamp <shaggy@linux.vnet.ibm.com>]

On Mon, 2006-12-18 at 19:51 +0100, Eric Sesterhenn wrote:
> hi,
> 
> while playing around with fsfuzzer, i got the following oops with jfs:
> 
> [  851.804875] BUG at fs/jfs/jfs_xtree.c:760 assert(!BT_STACK_FULL(btstack))
> [  851.805179] ------------[ cut here ]------------
> [  851.805238] kernel BUG at fs/jfs/jfs_xtree.c:760!

...

> On a damaged filesystem we might have a full stack and should
> not progress further, and return instead of calling BUG()
> 
> Signed-off-by: Eric Sesterhenn
> 
> --- linux-2.6.19/fs/jfs/jfs_xtree.c.orig	2006-12-18 14:37:07.000000000 +0100
> +++ linux-2.6.19/fs/jfs/jfs_xtree.c	2006-12-18 14:37:55.000000000 +0100
> @@ -757,6 +757,8 @@ static int xtSearch(struct inode *ip, s6
>  			nsplit = 0;
>  
>  		/* push (bn, index) of the parent page/entry */
> +		if (BT_STACK_FULL(btstack))
> +			return -EINVAL;

This leaks a reference on an xtree page.  I'd also like to mark the
superblock dirty here, so that fsck.jfs will fix the file system on the
next boot.  jfs_error does this as well as the requested error action.
The default is to remount read-only.

>  		BT_PUSH(btstack, bn, index);
>  
>  		/* get the child page block number */
> 

Do you want to retry your fsfuzzer testing with this patch?  I'm going
to take a look at the other calls to BT_PUSH in xtTruncate and
xtTruncate_pmap, but I'm too busy now, so I'll send you what I have so
far (untested).

Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>

diff --git a/fs/jfs/jfs_xtree.c b/fs/jfs/jfs_xtree.c
index e98eb03..176e984 100644
--- a/fs/jfs/jfs_xtree.c
+++ b/fs/jfs/jfs_xtree.c
@@ -757,6 +757,11 @@ static int xtSearch(struct inode *ip, s64 xoff,	s64 *nextp,
 			nsplit = 0;
 
 		/* push (bn, index) of the parent page/entry */
+		if (BT_STACK_FULL(btstack)) {
+			jfs_error(ip->i_sb, "stack overrun in xtSearch!");
+			XT_PUTPAGE(mp);
+			return -EIO;
+		}
 		BT_PUSH(btstack, bn, index);
 
 		/* get the child page block number */

-- 
David Kleikamp
IBM Linux Technology Center