linux-kernel - [62/75] llc: llc_cmsg_rcv was getting called after sk_eat

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Message-Id: <20120103223326.273232554@clark.kroah.org>
Date:	Tue, 03 Jan 2012 14:33:35 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Alexandru Juncu <ajuncu@...acom.com>,
	Kunjan Naik <knaik@...acom.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [62/75] llc: llc_cmsg_rcv was getting called after sk_eat_skb.

3.1-stable review patch.  If anyone has any objections, please let me know.

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


From: Alex Juncu <ajuncu@...acom.com>

[ Upstream commit 9cef310fcdee12b49b8b4c96fd8f611c8873d284 ]

Received non stream protocol packets were calling llc_cmsg_rcv that used a
skb after that skb was released by sk_eat_skb. This caused received STP
packets to generate kernel panics.

Signed-off-by: Alexandru Juncu <ajuncu@...acom.com>
Signed-off-by: Kunjan Naik <knaik@...acom.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 net/llc/af_llc.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -833,15 +833,15 @@ static int llc_ui_recvmsg(struct kiocb *
 		copied += used;
 		len -= used;
 
+		/* For non stream protcols we get one packet per recvmsg call */
+		if (sk->sk_type != SOCK_STREAM)
+			goto copy_uaddr;
+
 		if (!(flags & MSG_PEEK)) {
 			sk_eat_skb(sk, skb, 0);
 			*seq = 0;
 		}
 
-		/* For non stream protcols we get one packet per recvmsg call */
-		if (sk->sk_type != SOCK_STREAM)
-			goto copy_uaddr;
-
 		/* Partial read */
 		if (used + offset < skb->len)
 			continue;
@@ -857,6 +857,12 @@ copy_uaddr:
 	}
 	if (llc_sk(sk)->cmsg_flags)
 		llc_cmsg_rcv(msg, skb);
+
+	if (!(flags & MSG_PEEK)) {
+			sk_eat_skb(sk, skb, 0);
+			*seq = 0;
+	}
+
 	goto out;
 }
 


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