linux-kernel - [PATCH 1/2] Revert "af_unix: dont send SCM

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Date:	Wed, 03 Apr 2013 19:13:35 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"David S. Miller" <davem@...emloft.net>
Cc:	Sven Joachim <svenjoac@....de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Ding Tianhong <dingtianhong@...wei.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Andy Lutomirski <luto@...capital.net>,
	Karel Srot <ksrot@...hat.com>, <netdev@...r.kernel.org>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH 1/2] Revert "af_unix: dont send SCM_CREDENTIAL when dest socket is NULL"


This reverts commit 14134f6584212d585b310ce95428014b653dfaf6.

The problem that the above patch was meant to address is that af_unix
messages are not being coallesced because we are sending unnecesarry
credentials.  Not sending credentials in maybe_add_creds totally
breaks unconnected unix domain sockets that wish to send credentails
to other sockets.

In practice this break some versions of udev because they receive a
message and the sending uid is bogus so they drop the message.

Cc: stable@...r.kernel.org
Reported-by: Sven Joachim <svenjoac@....de>
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 net/unix/af_unix.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 971282b..f153a8d 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1412,8 +1412,8 @@ static void maybe_add_creds(struct sk_buff *skb, const struct socket *sock,
 	if (UNIXCB(skb).cred)
 		return;
 	if (test_bit(SOCK_PASSCRED, &sock->flags) ||
-	    (other->sk_socket &&
-	    test_bit(SOCK_PASSCRED, &other->sk_socket->flags))) {
+	    !other->sk_socket ||
+	    test_bit(SOCK_PASSCRED, &other->sk_socket->flags)) {
 		UNIXCB(skb).pid  = get_pid(task_tgid(current));
 		UNIXCB(skb).cred = get_current_cred();
 	}
-- 
1.7.5.4

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