linux-kernel - Re: [PATCH V3] jfs: check if leafidx greater than num leaves per dmap tree

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Message-ID: <d2feb9bf-5c14-4d43-a089-51514d182543@oracle.com>
Date: Tue, 27 Aug 2024 11:23:13 -0500
From: Dave Kleikamp <dave.kleikamp@...cle.com>
To: Edward Adam Davis <eadavis@...com>
Cc: jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        syzbot+dca05492eff41f604890@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH V3] jfs: check if leafidx greater than num leaves per dmap
 tree

On 8/23/24 8:25PM, Edward Adam Davis wrote:
> syzbot report a out of bounds in dbSplit, it because dmt_leafidx greater
> than num leaves per dmap tree, add a checking for dmt_leafidx in dbFindLeaf.
> 
> Reported-and-tested-by: syzbot+dca05492eff41f604890@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=dca05492eff41f604890
> Signed-off-by: Edward Adam Davis <eadavis@...com>
> ---
> V2 -> V3: Exclude control page
> 
>   fs/jfs/jfs_dmap.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
> index cb3cda1390ad..516bac758053 100644
> --- a/fs/jfs/jfs_dmap.c
> +++ b/fs/jfs/jfs_dmap.c
> @@ -2976,6 +2976,8 @@ static int dbFindLeaf(dmtree_t *tp, int l2nb, int *leafidx, bool is_ctl)
>   		 */
>   		assert(n < 4);
>   	}
> +	if (!is_ctl && le32_to_cpu(tp->dmt_leafidx) >= LPERDMAP)
> +		return -ENOSPC;
>   
>   	/* set the return to the leftmost leaf describing sufficient
>   	 * free space.

I was thinking something more along the lines of this.

jfs: check if leafidx greater than num leaves per dmap tree

syzbot report a out of bounds in dbSplit, it because dmt_leafidx greater
than num leaves per dmap tree, add a checking for dmt_leafidx in dbFindLeaf.

Shaggy:
Modified sanity check to apply to control pages as well as leaf pages.

Reported-and-tested-by: syzbot+dca05492eff41f604890@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=dca05492eff41f604890
Signed-off-by: Edward Adam Davis <eadavis@...com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@...cle.com>
---
  fs/jfs/jfs_dmap.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 8847e8c5d5b4..974ecf5e0d95 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -2944,9 +2944,10 @@ static void dbAdjTree(dmtree_t *tp, int leafno, int newval, bool is_ctl)
  static int dbFindLeaf(dmtree_t *tp, int l2nb, int *leafidx, bool is_ctl)
  {
  	int ti, n = 0, k, x = 0;
-	int max_size;
+	int max_size, max_idx;
  
  	max_size = is_ctl ? CTLTREESIZE : TREESIZE;
+	max_idx = is_ctl ? LPERCTL : LPERDMAP;
  
  	/* first check the root of the tree to see if there is
  	 * sufficient free space.
@@ -2978,6 +2979,8 @@ static int dbFindLeaf(dmtree_t *tp, int l2nb, int *leafidx, bool is_ctl)
  		 */
  		assert(n < 4);
  	}
+	if (le32_to_cpu(tp->dmt_leafidx) >= max_idx)
+		return -ENOSPC;
  
  	/* set the return to the leftmost leaf describing sufficient
  	 * free space.
-- 
2.46.0