From 3bba8cec6b83b6834bb7c53d91dedc5d2663058f Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Thu, 1 Nov 2018 12:02:37 -0700 Subject: [PATCH] net: drop skb on failure in ip_check_defrag() Most callers of pskb_trim_rcsum() simply drop the skb when it fails, however, ip_check_defrag() still continues to pass the skb up to stack. This is suspicious. In ip_check_defrag(), after we learn the skb is an IP fragment, passing the skb to callers makes no sense, because callers expect fragments are defrag'ed on success. So, dropping the skb when we can't defrag it is reasonable. Note, prior to commit 7943627623eb, this is not a big problem as checksum will be fixed up anyway. After it, the checksum is not correct on failure. Found this during code review. Fixes: 7943627623eb ("net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends") Cc: Eric Dumazet Signed-off-by: Cong Wang Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/ip_fragment.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index 9b0158fa431f2..d6ee343fdb864 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -722,10 +722,14 @@ struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user) if (ip_is_fragment(&iph)) { skb = skb_share_check(skb, GFP_ATOMIC); if (skb) { - if (!pskb_may_pull(skb, netoff + iph.ihl * 4)) - return skb; - if (pskb_trim_rcsum(skb, netoff + len)) - return skb; + if (!pskb_may_pull(skb, netoff + iph.ihl * 4)) { + kfree_skb(skb); + return NULL; + } + if (pskb_trim_rcsum(skb, netoff + len)) { + kfree_skb(skb); + return NULL; + } memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); if (ip_defrag(net, skb, user)) return NULL; -- 2.39.5