From: Florian Westphal fw@strlen.de
[ Upstream commit 421c119f558761556afca6a62ad183bc2d8659e0 ]
Unfortunately some versions of gcc emit following warning: $ make net/xfrm/xfrm_output.o linux/compiler.h:252:20: warning: array subscript is above array bounds [-Warray-bounds] hook_head = rcu_dereference(net->nf.hooks_arp[hook]); ^~~~~~~~~~~~~~~~~~~~~ xfrm_output_resume passes skb_dst(skb)->ops->family as its 'pf' arg so compiler can't know that we'll never access hooks_arp[]. (NFPROTO_IPV4 or NFPROTO_IPV6 are only possible cases).
Avoid this by adding an explicit WARN_ON_ONCE() check.
This patch has no effect if the family is a compile-time constant as gcc will remove the switch() construct entirely.
Reported-by: David Ahern dsahern@gmail.com Signed-off-by: Florian Westphal fw@strlen.de Reviewed-by: David Ahern dsahern@gmail.com Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/netfilter.h | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h index dd2052f0efb7..11b7b8ab0696 100644 --- a/include/linux/netfilter.h +++ b/include/linux/netfilter.h @@ -215,6 +215,8 @@ static inline int nf_hook(u_int8_t pf, unsigned int hook, struct net *net, break; case NFPROTO_ARP: #ifdef CONFIG_NETFILTER_FAMILY_ARP + if (WARN_ON_ONCE(hook >= ARRAY_SIZE(net->nf.hooks_arp))) + break; hook_head = rcu_dereference(net->nf.hooks_arp[hook]); #endif break;