tcp: make tcp_read_sock() more robust

stable inclusion
from linux-4.19.236
commit 9c90c0c62b5b5878f32400338983878a5345b050
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5646A
CVE: NA

--------------------------------

[ Upstream commit e3d5ea2c ]

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: NEric Dumazet <edumazet@google.com>
Acked-by: NJohn Fastabend <john.fastabend@gmail.com>
Acked-by: NJakub Sitnicki <jakub@cloudflare.com>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20220302161723.3910001-2-eric.dumazet@gmail.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

net/ipv4/tcp.c

@@ -1674,11 +1674,13 @@ 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