[62/75] llc: llc_cmsg_rcv was getting called after sk_eat_skb.

From: Greg KH
Date: Tue Jan 03 2012 - 17:41:53 EST


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

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


From: Alex Juncu <ajuncu@xxxxxxxxxxx>

[ 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@xxxxxxxxxxx>
Signed-off-by: Kunjan Naik <knaik@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
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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