Commit 479f5547 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

tcp: fix mem under-charging with zerocopy sendmsg() 



We got reports of following warning in inet_sock_destruct()

	WARN_ON(sk_forward_alloc_get(sk));

Whenever we add a non zero-copy fragment to a pure zerocopy skb,
we have to anticipate that whole skb->truesize will be uncharged
when skb is finally freed.

skb->data_len is the payload length. But the memory truesize
estimated by __zerocopy_sg_from_iter() is page aligned.

Fixes: 9b65b17d ("net: avoid double accounting for pure zerocopy skbs")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Talal Ahmad <talalahmad@google.com>
Cc: Arjun Roy <arjunroy@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Acked-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Link: https://lore.kernel.org/r/20220201065254.680532-1-eric.dumazet@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent e42e70ad

net/ipv4/tcp.c

+5 −2
Original line number Diff line number Diff line
@@ -1322,10 +1322,13 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) 


			/* skb changing from pure zc to mixed, must charge zc */

			if (unlikely(skb_zcopy_pure(skb))) {

				if (!sk_wmem_schedule(sk, skb->data_len))

				u32 extra = skb->truesize -

					    SKB_TRUESIZE(skb_end_offset(skb));



				if (!sk_wmem_schedule(sk, extra))

					goto wait_for_space;



				sk_mem_charge(sk, skb->data_len);

				sk_mem_charge(sk, extra);

				skb_shinfo(skb)->flags &= ~SKBFL_PURE_ZEROCOPY;

			}