[PATCH 3.5 59/64] net: fix cipso packet validation when !NETLABEL

[Luis Henriques]

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

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

From: Seif Mazareeb <seif@xxxxxxxxxxx>

commit f2e5ddcc0d12f9c4c7b254358ad245c9dddce13b upstream.

When CONFIG_NETLABEL is disabled, the cipso_v4_validate() function could loop
forever in the main loop if opt[opt_iter +1] == 0, this will causing a kernel
crash in an SMP system, since the CPU executing this function will
stall /not respond to IPIs.

This problem can be reproduced by running the IP Stack Integrity Checker
(http://isic.sourceforge.net) using the following command on a Linux machine
connected to DUT:

"icmpsic -s rand -d <DUT IP address> -r 123456"
wait (1-2 min)

Signed-off-by: Seif Mazareeb <seif@xxxxxxxxxxx>
Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 include/net/cipso_ipv4.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/net/cipso_ipv4.h b/include/net/cipso_ipv4.h
index a7a683e..a8c2ef6 100644
--- a/include/net/cipso_ipv4.h
+++ b/include/net/cipso_ipv4.h
@@ -290,6 +290,7 @@ static inline int cipso_v4_validate(const struct sk_buff *skb,
 	unsigned char err_offset = 0;
 	u8 opt_len = opt[1];
 	u8 opt_iter;
+	u8 tag_len;
 
 	if (opt_len < 8) {
 		err_offset = 1;
@@ -302,11 +303,12 @@ static inline int cipso_v4_validate(const struct sk_buff *skb,
 	}
 
 	for (opt_iter = 6; opt_iter < opt_len;) {
-		if (opt[opt_iter + 1] > (opt_len - opt_iter)) {
+		tag_len = opt[opt_iter + 1];
+		if ((tag_len == 0) || (opt[opt_iter + 1] > (opt_len - opt_iter))) {
 			err_offset = opt_iter + 1;
 			goto out;
 		}
-		opt_iter += opt[opt_iter + 1];
+		opt_iter += tag_len;
 	}
 
 out:
-- 
1.8.3.2

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