linux-kernel - Re: [PATCH V2] limit minixfs printks on corrupted dir i

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Date:	Thu, 09 Aug 2007 17:08:05 -0500
From:	Eric Sandeen <sandeen@...deen.net>
To:	7eggert@....de
CC:	linux-kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH V2] limit minixfs printks on corrupted dir i_size, CVE-2006-6058

Bodo Eggert wrote:

> Warning: I'm only looking at the patch.
> 
> You are supposed to print an error message for a user, not to write in a
> chat window to a 1337 script kiddie. OK, you just matched the current style,
> and your patch is IMHO OK for a quick security fix, but:
> 
> - Security fixes should be CCed to the security mailing list, shouldn't they?
>   (It might be security@ or stable@, I'll remember tomorrow, but then I'd
>    forget to comment)

ok.

> - Imagine you have three mounts containing a minix fs, how can you tell which
>   one is the the defective one?

good point.

> - The message says "minix_bmap", while the patch suggests it's in
>   block_to_path. Therefore I asume "minix_bmap" to have only random
>   informational value.

Yup, you're right.

> - Does block < 0 or block > $size make a difference?

well, block > size is likely to arrive from a corrupt i_size, and the
insistence upon going ahead and checking the next page after
encountering an error on the last one... I don't have any scenario in
mind where we'd be repeatedly trying to check blocks < 0.

> - the printk lacks the loglevel.

As do all other printk's in minixfs... (hm and 11,619 other printk's in
the kernel :) )

> - Asuming minix supports error handling, shouldn't it do something?
> 
> I'd suggest a message saying something like "minix: Bad block address on
> device 08:15, needs fsck".

Fair enough, as you said I was just fixing up the issue, not rewriting
the code around it.  But yes, I should probably have considered at least
a better message here.  I can fix this up & resend.  But I'm not
promising to audit all other printk's in minixfs this time around.  ;-)

-Eric
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