Re: [PATCH] jfs: array-index-out-of-bounds fix in dtReadFirst

[Dave Kleikamp]

On 9/28/24 3:37AM, Ghanshyam Agrawal wrote:
> The value of stbl can be sometimes out of bounds due
> to a bad filesystem. Added a check with appopriate return
> of error code in that case.
>
> Reported-by: syzbot+65fa06e29859e41a83f3@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=65fa06e29859e41a83f3
> Signed-off-by: Ghanshyam Agrawal <ghanshyam1898@xxxxxxxxx>
> ---
>   fs/jfs/jfs_dtree.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/fs/jfs/jfs_dtree.c b/fs/jfs/jfs_dtree.c
> index 5d3127ca68a4..69fd936fbdb3 100644
> --- a/fs/jfs/jfs_dtree.c
> +++ b/fs/jfs/jfs_dtree.c
> @@ -3086,6 +3086,13 @@ static int dtReadFirst(struct inode *ip, struct btstack * btstack)
>   
>   		/* get the leftmost entry */
>   		stbl = DT_GETSTBL(p);
> +
> +		if (stbl[0] < 0 || stbl[0] > 127) {

Technically, a signed 8-bit integer cannot exceed 127, but since the 
compiler will know that and optimize it out, I'll leave it in because it 
looks more complete.

> +			DT_PUTPAGE(mp);
> +			jfs_error(ip->i_sb, "stbl[0] out of bound\n");
> +			return -EIO;
> +		}
> +
>   		xd = (pxd_t *) & p->slot[stbl[0]];
>   
>   		/* get the child page block address */

Looks good. I'll apply this.

Shaggy