From: Eric Dumazet <edumazet@google.com>
Date: Wed, 2 Mar 2022 08:17:23 -0800
Subject: tcp: make tcp_read_sock() more robust
Patch-mainline: v5.17-rc7
Git-commit: e3d5ea2c011ecb16fb94c56a659364e6b30fac94
References: jsc#PED-1368

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>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 net/ipv4/tcp.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1694,11 +1694,13 @@ int tcp_read_sock(struct sock *sk, read_
 				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