From: Eric Dumazet edumazet@google.com
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 edumazet@google.com Cc: Mat Martineau mathew.j.martineau@linux.intel.com Cc: Talal Ahmad talalahmad@google.com Cc: Arjun Roy arjunroy@google.com Cc: Willem de Bruijn willemb@google.com Acked-by: Soheil Hassas Yeganeh soheil@google.com Acked-by: Paolo Abeni pabeni@redhat.com Link: https://lore.kernel.org/r/20220201184640.756716-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/tcp_input.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1652,6 +1652,8 @@ static struct sk_buff *tcp_shift_skb_dat (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))