From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 2/2] ext2: Avoid rec_len overflow with 64KB block size
Date: Wed, 17 Oct 2007 21:07:08 -0700
Message-ID: <20071017210708.75011e02.akpm@linux-foundation.org>
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Cc: cmm@us.ibm.com, linux-ext4@vger.kernel.org,
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To: Jan Kara <jack@suse.cz>
In-Reply-To: <20071011111849.GC7125@duck.suse.cz>
Sender: linux-ext4-owner@vger.kernel.org

On Thu, 11 Oct 2007 13:18:49 +0200 Jan Kara <jack@suse.cz> wrote:

> +static inline __le16 ext2_rec_len_to_disk(unsigned len)
> +{
> +	if (len == (1 << 16))
> +		return cpu_to_le16(EXT2_MAX_REC_LEN);
> +	else if (len > (1 << 16))
> +		BUG();
> +	return cpu_to_le16(len);
> +}

Of course, ext2 shouldn't be trying to write a bad record length into a
directory entry.  But are we sure that there is no way in which this
situation could occur is the on-disk data was _already_ bad?

Because it is very bad for a fileysstem to go BUG in response to unexpected
data on the disk.