linux-ext4 - Re: [PATCH 2/2] ext4: handle errors in ext4_clear

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Message-ID: <20110321013749.GE4135@thunk.org>
Date:	Sun, 20 Mar 2011 21:37:49 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Amir Goldstein <amir73il@...il.com>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 2/2] ext4: handle errors in ext4_clear_blocks()

On Tue, Mar 01, 2011 at 02:28:26PM +0200, Amir Goldstein wrote:
> +out_err:
> +	ext4_std_error(inode->i_sb, err);
> +	return err;

Umm, you do realize this function will mark the file system as dirty,
and possibly remount the file system read-only, or panic the system,
right?

That's appropriate for normal journal failures (since there's no
recovering from them), but if you're proposing that a simple lack of
free blocks when doing a COW operation will result in a ENOSPC, all a
malicious userspace application needs to do to potentially bring the
system down is to attempt to unlink or truncate a file while COW
snapshots are enabled.....

Do you really want me to include this patch?  I think you may want to
rethink how you want to handle this case....

						- Ted
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