linux-kernel - Re: [PATCH] jfs: Fix array-index-out-of-bounds in diFree

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Date: Thu, 25 Apr 2024 15:17:04 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Jeongjun Park <aha310510@...il.com>
Cc: brauner@...nel.org, jfs-discussion@...ts.sourceforge.net,
	jlayton@...nel.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, shaggy@...nel.org,
	syzbot+241c815bda521982cb49@...kaller.appspotmail.com,
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] jfs: Fix array-index-out-of-bounds in diFree

On Thu, Apr 25, 2024 at 11:10:38PM +0900, Jeongjun Park wrote:
> Matthew Wilcox wrote:
> > If that's the problem then the correct place to detect & reject this is
> > during mount, not at inode free time.
> 
> I fixed the patch as you said. If you patch in this way, the 
> file system will not be affected by the vulnerability at all 
> due to the code structure.

It should be checked earlier than this.  There's this code in
dbMount().  Why isn't this catching it?

        bmp->db_agl2size = le32_to_cpu(dbmp_le->dn_agl2size);
        if (bmp->db_agl2size > L2MAXL2SIZE - L2MAXAG ||
            bmp->db_agl2size < 0) {
                err = -EINVAL;
                goto err_release_metapage;
        }

        if (((bmp->db_mapsize - 1) >> bmp->db_agl2size) > MAXAG) {
                err = -EINVAL;
                goto err_release_metapage;
        }


> Thanks.
> 
> ---
>  fs/jfs/jfs_imap.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
> index 2ec35889ad24..ba0aa2f145cc 100644
> --- a/fs/jfs/jfs_imap.c
> +++ b/fs/jfs/jfs_imap.c
> @@ -290,7 +290,7 @@ int diSync(struct inode *ipimap)
>  int diRead(struct inode *ip)
>  {
>  	struct jfs_sb_info *sbi = JFS_SBI(ip->i_sb);
> -	int iagno, ino, extno, rc;
> +	int iagno, ino, extno, rc, agno;
>  	struct inode *ipimap;
>  	struct dinode *dp;
>  	struct iag *iagp;
> @@ -339,6 +339,9 @@ int diRead(struct inode *ip)
>  
>  	/* get the ag for the iag */
>  	agstart = le64_to_cpu(iagp->agstart);
> +	agno = BLKTOAG(agstart, JFS_SBI(ip->i_sb));
> +	if(agno >= MAXAG || agno < 0)
> +		return -EIO;
>  
>  	release_metapage(mp);
>  
> -- 
> 2.34.1