linux-kernel - Re: [GIT PULL] s390 patches for 2.6.39-rc4

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Date:	Tue, 26 Apr 2011 11:38:22 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-s390 <linux-s390@...r.kernel.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [GIT PULL] s390 patches for 2.6.39-rc4

I'll pull this, but:

On Tue, Apr 26, 2011 at 2:03 AM, Martin Schwidefsky
<schwidefsky@...ibm.com> wrote:
>
> Jan Glauber (3):
>      [S390] prng: prevent access beyond end of stack

I don't think that's _still_ correct.

Just looking at the diff, it looks broken:

>        /* Add the entropy */
>        while (nbytes >= 8) {
> -               *((__u64 *)parm_block) ^= *((__u64 *)buf+i*8);
> +               *((__u64 *)parm_block) ^= *((__u64 *)buf+i);
>                prng_add_entropy();
>                i += 8;
>                nbytes -= 8;

The "i += 8" implies that "i" is a byte offset.

But "(__u64 *)buf+i" will parse as "((__u64 *)buf) + i" and thus still
do another multiply-by-eight.

So the diff fixes one "off by a factor of 8", but not another, if I
read it right.

So the parenthesis should be moved around to something like "*(__u64
*) (buf+i)", I think.

                     Linus
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