re: netfilter: nfnetlink_log: send complete hardware header

re: netfilter: nfnetlink_log: send complete hardware header

[Dan Carpenter]

Hi,

Smatch complains abbout 72961ecf84d67d6 "netfilter: nfnetlink_log: send
complete hardware header" which is net-next.
    
   462          if (indev && skb->dev) {
                             ^^^^^^^^
	skb->dev can be NULL here.

   463                  struct nfulnl_msg_packet_hw phw;
   464                  int len = dev_parse_header(skb, phw.hw_addr);
   465                  if (len > 0) {
   466                          phw.hw_addrlen = htons(len);
   467                          NLA_PUT(inst->skb, NFULA_HWADDR, sizeof(phw), &phw);
   468                  }
   469          }
   470  
   471          if (indev && skb_mac_header_was_set(skb)) {
   472                  NLA_PUT_BE16(inst->skb, NFULA_HWTYPE, htons(skb->dev->type));
                                                                    ^^^^^^^^
	It's dereferenced here.

   473                  NLA_PUT_BE16(inst->skb, NFULA_HWLEN,
   474                               htons(skb->dev->hard_header_len));

I'm not sure how you want to deal with this.

regards,
dan carpenter

[PATCH] netfilter: nfnetlink_log: Fix potential problem if skb->dev is null

[Eric Leblond]

This patch fixes a potentiel problem pointed out by Dan Carpenter
using smatch: skb->dev is used but there is no test on nullity
of pointer. It may not express as if mac header is filled we can
think that the dev is also set.
---
 net/netfilter/nfnetlink_log.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 6a1572b..b5617c2 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -468,7 +468,7 @@ __build_packet_message(struct nfulnl_instance *inst,
 		}
 	}
 
-	if (indev && skb_mac_header_was_set(skb)) {
+	if (indev && skb->dev && skb_mac_header_was_set(skb)) {
 		NLA_PUT_BE16(inst->skb, NFULA_HWTYPE, htons(skb->dev->type));
 		NLA_PUT_BE16(inst->skb, NFULA_HWLEN,
 			     htons(skb->dev->hard_header_len));
-- 
1.6.1