From ac9e70b17ecd7c6e933ff2eaf7ab37429e71bf4d Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 2 Nov 2016 07:53:17 -0700 Subject: tcp: fix potential memory corruption MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Imagine initial value of max_skb_frags is 17, and last skb in write queue has 15 frags. Then max_skb_frags is lowered to 14 or smaller value. tcp_sendmsg() will then be allowed to add additional page frags and eventually go past MAX_SKB_FRAGS, overflowing struct skb_shared_info. Fixes: 5f74f82ea34c ("net:Add sysctl_max_skb_frags") Signed-off-by: Eric Dumazet Cc: Hans Westgaard Ry Cc: Håkon Bugge Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/ipv4/tcp.c') diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 3251fe71f39f..18238ef8135a 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1241,7 +1241,7 @@ new_segment: if (!skb_can_coalesce(skb, i, pfrag->page, pfrag->offset)) { - if (i == sysctl_max_skb_frags || !sg) { + if (i >= sysctl_max_skb_frags || !sg) { tcp_mark_push(tp, skb); goto new_segment; } -- cgit v1.2.3 From 79d8665b9545e128637c51cf7febde9c493b6481 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 2 Nov 2016 14:41:50 -0700 Subject: tcp: fix return value for partial writes After my commit, tcp_sendmsg() might restart its loop after processing socket backlog. If sk_err is set, we blindly return an error, even though we copied data to user space before. We should instead return number of bytes that could be copied, otherwise user space might resend data and corrupt the stream. This might happen if another thread is using recvmsg(MSG_ERRQUEUE) to process timestamps. Issue was diagnosed by Soheil and Willem, big kudos to them ! Fixes: d41a69f1d390f ("tcp: make tcp_sendmsg() aware of socket backlog") Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Cc: Soheil Hassas Yeganeh Cc: Yuchung Cheng Cc: Neal Cardwell Tested-by: Soheil Hassas Yeganeh Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/ipv4/tcp.c') diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 18238ef8135a..814af89c1bd3 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1164,7 +1164,7 @@ restart: err = -EPIPE; if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)) - goto out_err; + goto do_error; sg = !!(sk->sk_route_caps & NETIF_F_SG); -- cgit v1.2.3