The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 358ed624207012f03318235017ac6fb41f8af592 Mon Sep 17 00:00:00 2001

From: Talal Ahmad talalahmad@google.com Date: Fri, 9 Jul 2021 11:43:06 -0400 Subject: [PATCH] tcp: call sk_wmem_schedule before sk_mem_charge in zerocopy path

sk_wmem_schedule makes sure that sk_forward_alloc has enough bytes for charging that is going to be done by sk_mem_charge.

In the transmit zerocopy path, there is sk_mem_charge but there was no call to sk_wmem_schedule. This change adds that call.

Without this call to sk_wmem_schedule, sk_forward_alloc can go negetive which is a bug because sk_forward_alloc is a per-socket space that has been forward charged so this can't be negative.

Fixes: f214f915e7db ("tcp: enable MSG_ZEROCOPY") Signed-off-by: Talal Ahmad talalahmad@google.com Reviewed-by: Willem de Bruijn willemb@google.com Reviewed-by: Wei Wang weiwan@google.com Reviewed-by: Soheil Hassas Yeganeh soheil@google.com Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index d5ab5f243640..8cb44040ec68 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1375,6 +1375,9 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) } pfrag->offset += copy; } else { + if (!sk_wmem_schedule(sk, copy)) + goto wait_for_space; + err = skb_zerocopy_iter_stream(sk, skb, msg, copy, uarg); if (err == -EMSGSIZE || err == -EEXIST) { tcp_mark_push(tp, skb);