Re: [lvc-project] [PATCH] netfilter: nfnetlink: NULL-check skb->dev in __build_packet_message()

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On 3/27/23 13:22, Pablo Neira Ayuso wrote:
On Mon, Mar 27, 2023 at 12:41:16PM +0300, Igor Artemiev wrote:
After having been compared to NULL value at nfnetlink_log.c:560,
pointer 'skb->dev' is dereferenced at nfnetlink_log.c:576.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Igor Artemiev <Igor.A.Artemiev@xxxxxxx>
---
  net/netfilter/nfnetlink_log.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index d97eb280cb2e..2711509eb9a5 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -572,7 +572,7 @@ __build_packet_message(struct nfnl_log_net *log,
  		}
  	}
- if (indev && skb_mac_header_was_set(skb)) {
+	if (indev && skb->dev && skb_mac_header_was_set(skb)) {
This cannot ever happen, we assume skb->dev is always set on.

  		if (nla_put_be16(inst->skb, NFULA_HWTYPE, htons(skb->dev->type)) ||
  		    nla_put_be16(inst->skb, NFULA_HWLEN,
  				 htons(skb->dev->hard_header_len)))
--
2.30.2


If skb->dev is always set on, should the check at nfnetlink_log.c:560 be removed?
|

if  (indev  &&  skb->dev  &&
	skb_mac_header_was_set(skb)  &&
	    	skb_mac_header_len(skb)  !=  0)  { |

||Thanks, Igor




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