linux-kernel - Re: [PATCH v3] jfs: validate max amount of blocks before allocation.

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Date:   Sun, 23 Jul 2023 15:40:03 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Aleksei Filippov <halip0503@...il.com>
Cc:     jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        shaggy@...nel.org,
        syzbot+5f088f29593e6b4c8db8@...kaller.appspotmail.com
Subject: Re: [PATCH v3] jfs: validate max amount of blocks before allocation.

On Sun, Jul 23, 2023 at 04:29:59PM +0300, Aleksei Filippov wrote:
> From: Alexei Filippov <halip0503@...il.com>
> 
> The lack of checking bmp->db_max_freebud in extBalloc() can lead to
> shift out of bounds, so this patch prevents undefined behavior, because
> bmp->db_max_freebud == -1 only if there is no free space.
> 
> Signed-off-by: Aleksei Filippov <halip0503@...il.com>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-and-tested-by: syzbot+5f088f29593e6b4c8db8@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?id=01abadbd6ae6a08b1f1987aa61554c6b3ac19ff2
> ---
>  fs/jfs/jfs_extent.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/fs/jfs/jfs_extent.c b/fs/jfs/jfs_extent.c
> index ae99a7e232ee..a82751e6c47f 100644
> --- a/fs/jfs/jfs_extent.c
> +++ b/fs/jfs/jfs_extent.c
> @@ -311,6 +311,11 @@ extBalloc(struct inode *ip, s64 hint, s64 * nblocks, s64 * blkno)
>  	 * blocks in the map. in that case, we'll start off with the
>  	 * maximum free.
>  	 */
> +
> +	/* give up if no space left */
> +	if (bmp->db_maxfreebud == -1)
> +		return -ENOSPC;
> +
>  	max = (s64) 1 << bmp->db_maxfreebud;
>  	if (*nblocks >= max && *nblocks > nbperpage)
>  		nb = nblks = (max > nbperpage) ? max : nbperpage;
> -- 
> 2.25.1
> 
> Fix commit message.

The --- information for the version goes below the first --- line, not
the last.  Look at the examples on the mailing lists for the proper
format.

thanks,

greg k-h