From c3d81231ab84db96fe80f78e9432c285da1ab86c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 1 Feb 2022 10:46:40 -0800 Subject: [PATCH] tcp: add missing tcp_skb_can_collapse() test in tcp_shift_skb_data() commit b67985be400969578d4d4b17299714c0e5d2c07b upstream. tcp_shift_skb_data() might collapse three packets into a larger one. P_A, P_B, P_C -> P_ABC Historically, it used a single tcp_skb_can_collapse_to(P_A) call, because it was enough. In commit 85712484110d ("tcp: coalesce/collapse must respect MPTCP extensions"), this call was replaced by a call to tcp_skb_can_collapse(P_A, P_B) But the now needed test over P_C has been missed. This probably broke MPTCP. Then later, commit 9b65b17db723 ("net: avoid double accounting for pure zerocopy skbs") added an extra condition to tcp_skb_can_collapse(), but the missing call from tcp_shift_skb_data() is also breaking TCP zerocopy, because P_A and P_C might have different skb_zcopy_pure() status. Fixes: 85712484110d ("tcp: coalesce/collapse must respect MPTCP extensions") Fixes: 9b65b17db723 ("net: avoid double accounting for pure zerocopy skbs") Signed-off-by: Eric Dumazet Cc: Mat Martineau Cc: Talal Ahmad Cc: Arjun Roy Cc: Willem de Bruijn Acked-by: Soheil Hassas Yeganeh Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20220201184640.756716-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp_input.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index f3b6239674361..509f577869d4e 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1652,6 +1652,8 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, (mss != tcp_skb_seglen(skb))) goto out; + if (!tcp_skb_can_collapse(prev, skb)) + goto out; len = skb->len; pcount = tcp_skb_pcount(skb); if (tcp_skb_shift(prev, skb, pcount, len))