linux-kernel - Re: [PATCH] jfs: fix array-index-out-of-bounds

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Message-ID: <c9f80af9-4cf0-4b6e-8c61-4b7a6f287cd9@wanadoo.fr>
Date: Sun, 22 Sep 2024 17:05:01 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Ghanshyam Agrawal <ghanshyam1898@...il.com>, shaggy@...nel.org,
 ghandatmanas@...il.com, jlayton@...nel.org, eadavis@...com,
 brauner@...nel.org
Cc: jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
 syzbot+808f3f84407f08a93022@...kaller.appspotmail.com
Subject: Re: [PATCH] jfs: fix array-index-out-of-bounds

Le 22/09/2024 à 13:00, Ghanshyam Agrawal a écrit :
> In some cases, dn_numag may be greater than MAXAG which may
> result in an array-index-out-of-bounds in dbNextAG. Added
> a check to return an error code before we crash.
> 
> Reported-by: syzbot+808f3f84407f08a93022@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=808f3f84407f08a93022
> Signed-off-by: Ghanshyam Agrawal <ghanshyam1898@...il.com>
> ---
>   fs/jfs/jfs_imap.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
> index 2ec35889ad24..5088da13e8f1 100644
> --- a/fs/jfs/jfs_imap.c
> +++ b/fs/jfs/jfs_imap.c
> @@ -1360,6 +1360,9 @@ int diAlloc(struct inode *pip, bool dir, struct inode *ip)
>   	if (agno < 0 || agno > dn_numag)
>   		return -EIO;
>   
> +	if (unlikely(dn_numag > MAXAG))

Hi,

looking at other places with checks with MAXAG, I wonder if it should be >=?

CJ

> +		return -EIO;
> +
>   	if (atomic_read(&JFS_SBI(pip->i_sb)->bmap->db_active[agno])) {
>   		/*
>   		 * There is an open file actively growing.  We want to