Commit e2f67259 authored Jan 17, 2013 by Nickolai Zeldovich Committed by Steffen Klassert Jan 18, 2013

net/xfrm/xfrm_replay: avoid division by zero



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@csail.mit.edu>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

parent a9403f8a

net/xfrm/xfrm_replay.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -242,11 +242,13 @@ static void xfrm_replay_advance_bmp(struct xfrm_state *x, __be32 net_seq)
		u32 diff;
		struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
		u32 seq = ntohl(net_seq);
		u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
		u32 pos;

		if (!replay_esn->replay_window)
		return;

		pos = (replay_esn->seq - 1) % replay_esn->replay_window;

		if (seq > replay_esn->seq) {
		diff = seq - replay_esn->seq;