From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Alexei Starovoitov , "David S. Miller" Subject: [PATCH 3.12 07/19] tcp: gso: fix truesize tracking Date: Mon, 18 Nov 2013 10:37:20 -0800 Message-Id: <20131118183646.248381899@linuxfoundation.org> In-Reply-To: <20131118183644.030738675@linuxfoundation.org> References: <20131118183644.030738675@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 0d08c42cf9a71530fef5ebcfe368f38f2dd0476f ] commit 6ff50cd55545 ("tcp: gso: do not generate out of order packets") had an heuristic that can trigger a warning in skb_try_coalesce(), because skb->truesize of the gso segments were exactly set to mss. This breaks the requirement that skb->truesize >= skb->len + truesizeof(struct sk_buff); It can trivially be reproduced by : ifconfig lo mtu 1500 ethtool -K lo tso off netperf As the skbs are looped into the TCP networking stack, skb_try_coalesce() warns us of these skb under-estimating their truesize. Signed-off-by: Eric Dumazet Reported-by: Alexei Starovoitov Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp_offload.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) --- a/net/ipv4/tcp_offload.c +++ b/net/ipv4/tcp_offload.c @@ -18,6 +18,7 @@ struct sk_buff *tcp_tso_segment(struct s netdev_features_t features) { struct sk_buff *segs = ERR_PTR(-EINVAL); + unsigned int sum_truesize = 0; struct tcphdr *th; unsigned int thlen; unsigned int seq; @@ -102,13 +103,7 @@ struct sk_buff *tcp_tso_segment(struct s if (copy_destructor) { skb->destructor = gso_skb->destructor; skb->sk = gso_skb->sk; - /* {tcp|sock}_wfree() use exact truesize accounting : - * sum(skb->truesize) MUST be exactly be gso_skb->truesize - * So we account mss bytes of 'true size' for each segment. - * The last segment will contain the remaining. - */ - skb->truesize = mss; - gso_skb->truesize -= mss; + sum_truesize += skb->truesize; } skb = skb->next; th = tcp_hdr(skb); @@ -125,7 +120,9 @@ struct sk_buff *tcp_tso_segment(struct s if (copy_destructor) { swap(gso_skb->sk, skb->sk); swap(gso_skb->destructor, skb->destructor); - swap(gso_skb->truesize, skb->truesize); + sum_truesize += skb->truesize; + atomic_add(sum_truesize - gso_skb->truesize, + &skb->sk->sk_wmem_alloc); } delta = htonl(oldlen + (skb_tail_pointer(skb) -