linux-kernel - Re: [PATCH] net/xfrm/xfrm_replay: avoid division by zero

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Message-ID: <20130118085723.GG24987@secunet.com>
Date:	Fri, 18 Jan 2013 09:57:23 +0100
From:	Steffen Klassert <steffen.klassert@...unet.com>
To:	Nickolai Zeldovich <nickolai@...il.mit.edu>
Cc:	Herbert Xu <herbert@...dor.hengli.com.au>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/xfrm/xfrm_replay: avoid division by zero

On Thu, Jan 17, 2013 at 01:58:28PM -0500, Nickolai Zeldovich wrote:
> All of the xfrm_replay->advance functions in xfrm_replay.c check if
> x->replay_esn->replay_window is zero (and return if so).  However,
> one of them, xfrm_replay_advance_bmp(), divides by that value (in the
> '%' operator) before doing the check, which can potentially trigger
> a divide-by-zero exception.  Some compilers will also assume that the
> earlier division means the value cannot be zero later, and thus will
> eliminate the subsequent zero check as dead code.
> 
> This patch moves the division to after the check.
> 
> Signed-off-by: Nickolai Zeldovich <nickolai@...il.mit.edu>

Applied, thanks!
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