From 3819a35fdb8f82428c2b5190f195c4e0b8c427bf Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 13 Jan 2017 14:55:14 +0100 Subject: [PATCH] xfrm: fix possible null deref in xfrm_init_tempstate Dan reports following smatch warning: net/xfrm/xfrm_state.c:659 error: we previously assumed 'afinfo' could be null (see line 651) 649 struct xfrm_state_afinfo *afinfo = xfrm_state_afinfo_get_rcu(family); 651 if (afinfo) ... 658 } 659 afinfo->init_temprop(x, tmpl, daddr, saddr); I am resonably sure afinfo cannot be NULL here. xfrm_state4.c and state6.c are both part of ipv4/ipv6 (depends on CONFIG_XFRM, a boolean) but even if ipv6 is a module state6.c can't be removed (ipv6 lacks module_exit so it cannot be removed). The only callers for xfrm6_fini that leads to state backend unregister are error unwinding paths that can be called during ipv6 init function. So after ipv6 module is loaded successfully the state backend cannot go away anymore. The family value from policy lookup path is taken from dst_entry, so that should always be AF_INET(6). However, since this silences the warning and avoids readers of this code wondering about possible null deref it seems preferrable to be defensive and just add the old check back. Fixes: 711059b9752ad0 ("xfrm: add and use xfrm_state_afinfo_get_rcu") Reported-by: Dan Carpenter Signed-off-by: Florian Westphal Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_state.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index a62097e640b5..5a597dbbe564 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -648,8 +648,10 @@ xfrm_init_tempstate(struct xfrm_state *x, const struct flowi *fl, { struct xfrm_state_afinfo *afinfo = xfrm_state_afinfo_get_rcu(family); - if (afinfo) - afinfo->init_tempsel(&x->sel, fl); + if (!afinfo) + return; + + afinfo->init_tempsel(&x->sel, fl); if (family != tmpl->encap_family) { afinfo = xfrm_state_afinfo_get_rcu(tmpl->encap_family); -- 2.20.1