[PATCH 5.13 147/156] tcp: call sk_wmem_schedule before sk_mem_charge in zerocopy path

From: Greg Kroah-Hartman
Date: Thu Jul 22 2021 - 12:54:28 EST

From: Talal Ahmad <talalahmad@xxxxxxxxxx>

commit 358ed624207012f03318235017ac6fb41f8af592 upstream.

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@xxxxxxxxxx>
Reviewed-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Reviewed-by: Wei Wang <weiwan@xxxxxxxxxx>
Reviewed-by: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
net/ipv4/tcp.c | 3 +++
1 file changed, 3 insertions(+)

--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1375,6 +1375,9 @@ new_segment:
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);