linux-kernel - Re: [PATCH v5] jfs: validate max amount of blocks before allocation.

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Date:   Tue, 29 Aug 2023 12:28:14 -0500
From:   Dave Kleikamp <dave.kleikamp@...cle.com>
To:     Aleksei Filippov <halip0503@...il.com>, gregkh@...uxfoundation.org
Cc:     jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        syzbot+5f088f29593e6b4c8db8@...kaller.appspotmail.com
Subject: Re: [PATCH v5] jfs: validate max amount of blocks before allocation.

On 8/19/23 12:32PM, 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.

Thanks. Applied.

> 
> 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
> ---
> 
> Changes since v1:
> 	-Commit message fix. Add Fixes line.
> Changes since v2-v4:
> 	-Commit message fixes.
>   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;