tcp: properly reset skb->truesize for tx recycling

tcp sendmsg() and sendpage() normally advance skb->data_len and skb->truesize by the payload added to an skb. But sendmsg(fd, ..., MSG_ZEROCOPY) has to account for whole pages, even if a single byte of payload is used in the page. This means that we can not assume skb->truesize can be adjusted by skb->data_len. We must instead overwrite its value. Otherwise skb->truesize is too big and can hit socket sndbuf limit, especially if the skb is recycled multiple times :/ Fixes: 472c2e0 ("tcp: add one skb cache for tx") Signed-off-by: Eric Dumazet <[email protected]> Cc: Soheil Hassas Yeganeh <[email protected]> Cc: Willem de Bruijn <[email protected]> Acked-by: Soheil Hassas Yeganeh <[email protected]> Signed-off-by: David S. Miller <[email protected]>
josf · Apr 19, 2019 · d7cc399 · d7cc399
1 parent 0a9798c
commit d7cc399
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
@@ -868,7 +868,7 @@ struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp,
 	if (likely(!size)) {
 		skb = sk->sk_tx_skb_cache;
 		if (skb && !skb_cloned(skb)) {
-			skb->truesize -= skb->data_len;
+			skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));
 			sk->sk_tx_skb_cache = NULL;
 			pskb_trim(skb, 0);
 			INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);