[PATCH v6] af_unix: Read with MSG_PEEK loops if the first unread byte is OOB

[Rao Shoaib <Rao.Shoaib@oracle.com>]

Read with MSG_PEEK flag loops if the first byte to read is an OOB byte.
commit 22dd70eb2c3d ("af_unix: Don't peek OOB data without MSG_OOB.")
addresses the loop issue but does not address the issue that no data
beyond OOB byte can be read.

>>> from socket import *
>>> c1, c2 = socketpair(AF_UNIX, SOCK_STREAM)
>>> c1.send(b'a', MSG_OOB)
1
>>> c1.send(b'b')
1
>>> c2.recv(1, MSG_PEEK | MSG_DONTWAIT)
b'b'

>>> from socket import *
>>> c1, c2 = socketpair(AF_UNIX, SOCK_STREAM)
>>> c2.setsockopt(SOL_SOCKET, SO_OOBINLINE, 1)
>>> c1.send(b'a', MSG_OOB)
1
>>> c1.send(b'b')
1
>>> c2.recv(1, MSG_PEEK | MSG_DONTWAIT)
b'a'
>>> c2.recv(1, MSG_PEEK | MSG_DONTWAIT)
b'a'
>>> c2.recv(1, MSG_DONTWAIT)
b'a'
>>> c2.recv(1, MSG_PEEK | MSG_DONTWAIT)
b'b'
>>>

Fixes: 314001f0bf92 ("af_unix: Add OOB support")

Signed-off-by: Rao Shoaib <Rao.Shoaib@oracle.com>
---
 net/unix/af_unix.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 80846279de9f..5e695a9a609c 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2625,18 +2625,18 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
 		if (skb == u->oob_skb) {
 			if (copied) {
 				skb = NULL;
-			} else if (sock_flag(sk, SOCK_URGINLINE)) {
-				if (!(flags & MSG_PEEK)) {
+			} else if (!(flags & MSG_PEEK)) {
+				if (sock_flag(sk, SOCK_URGINLINE)) {
 					WRITE_ONCE(u->oob_skb, NULL);
 					consume_skb(skb);
+				} else {
+					__skb_unlink(skb, &sk->sk_receive_queue);
+					WRITE_ONCE(u->oob_skb, NULL);
+					unlinked_skb = skb;
+					skb = skb_peek(&sk->sk_receive_queue);
 				}
-			} else if (flags & MSG_PEEK) {
-				skb = NULL;
-			} else {
-				__skb_unlink(skb, &sk->sk_receive_queue);
-				WRITE_ONCE(u->oob_skb, NULL);
-				unlinked_skb = skb;
-				skb = skb_peek(&sk->sk_receive_queue);
+			} else if (!sock_flag(sk, SOCK_URGINLINE)) {
+				skb = skb_peek_next(skb, &sk->sk_receive_queue);
 			}
 		}
 
-- 
2.39.3