linux-kernel - [ 027/104] tools: hv: Netlink source address validation allows DoS

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Message-Id: <20130325010526.976899174@decadent.org.uk>
Date:	Mon, 25 Mar 2013 01:05:51 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, Tomas Hozza <thozza@...hat.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [ 027/104] tools: hv: Netlink source address validation allows DoS

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

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

From: Tomas Hozza <thozza@...hat.com>

commit 95a69adab9acfc3981c504737a2b6578e4d846ef upstream.

The source code without this patch caused hypervkvpd to exit when it processed
a spoofed Netlink packet which has been sent from an untrusted local user.
Now Netlink messages with a non-zero nl_pid source address are ignored
and a warning is printed into the syslog.

Signed-off-by: Tomas Hozza <thozza@...hat.com>
Acked-by:  K. Y. Srinivasan <kys@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 tools/hv/hv_kvp_daemon.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/tools/hv/hv_kvp_daemon.c
+++ b/tools/hv/hv_kvp_daemon.c
@@ -393,13 +393,19 @@ int main(void)
 		len = recvfrom(fd, kvp_recv_buffer, sizeof(kvp_recv_buffer), 0,
 				addr_p, &addr_l);
 
-		if (len < 0 || addr.nl_pid) {
+		if (len < 0) {
 			syslog(LOG_ERR, "recvfrom failed; pid:%u error:%d %s",
 					addr.nl_pid, errno, strerror(errno));
 			close(fd);
 			return -1;
 		}
 
+		if (addr.nl_pid) {
+			syslog(LOG_WARNING, "Received packet from untrusted pid:%u",
+					addr.nl_pid);
+			continue;
+		}
+
 		incoming_msg = (struct nlmsghdr *)kvp_recv_buffer;
 		incoming_cn_msg = (struct cn_msg *)NLMSG_DATA(incoming_msg);
 


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