From: Eric Dumazet <edumazet@google.com>
Date: Wed, 2 Mar 2022 16:17:23 +0000 (-0800)
Subject: tcp: make tcp_read_sock() more robust
X-Git-Tag: v4.19.236~44
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9c90c0c62b5b5878f32400338983878a5345b050;p=thirdparty%2Fkernel%2Fstable.git

tcp: make tcp_read_sock() more robust

[ Upstream commit e3d5ea2c011ecb16fb94c56a659364e6b30fac94 ]

If recv_actor() returns an incorrect value, tcp_read_sock()
might loop forever.

Instead, issue a one time warning and make sure to make progress.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20220302161723.3910001-2-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 4dce1b418acc2..f7795488b0adf 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1669,11 +1669,13 @@ int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
 				if (!copied)
 					copied = used;
 				break;
-			} else if (used <= len) {
-				seq += used;
-				copied += used;
-				offset += used;
 			}
+			if (WARN_ON_ONCE(used > len))
+				used = len;
+			seq += used;
+			copied += used;
+			offset += used;
+
 			/* If recv_actor drops the lock (e.g. TCP splice
 			 * receive) the skb pointer might be invalid when
 			 * getting here: tcp_collapse might have deleted it