From: Paul Moore <pmoore@xxxxxxxxxx>
-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
If you see a problem with using this for longterm, please comment.
-------------------
commit a9d0acf8d157c30374af76d43e7f05b5b108be0c upstream.
[ Upstream commit 89d7ae34cdda4195809a5a987f697a517a2a3177 ]
As reported by Alan Cox, and verified by Lin Ming, when a user
attempts to add a CIPSO option to a socket using the CIPSO_V4_TAG_LOCAL
tag the kernel dies a terrible death when it attempts to follow a NULL
pointer (the skb argument to cipso_v4_validate() is NULL when called via
the setsockopt() syscall).
This patch fixes this by first checking to ensure that the skb is
non-NULL before using it to find the incoming network interface. In
the unlikely case where the skb is NULL and the user attempts to add
a CIPSO option with the _TAG_LOCAL tag we return an error as this is
not something we want to allow.
A simple reproducer, kindly supplied by Lin Ming, although you must
have the CIPSO DOI #3 configure on the system first or you will be
caught early in cipso_v4_validate():
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <string.h>
struct local_tag {
char type;
char length;
char info[4];
};
struct cipso {
char type;
char length;
char doi[4];
struct local_tag local;
};
int main(int argc, char **argv)
{
int sockfd;
struct cipso cipso = {
.type = IPOPT_CIPSO,
.length = sizeof(struct cipso),
.local = {
.type = 128,
.length = sizeof(struct local_tag),
},
};
memset(cipso.doi, 0, 4);
cipso.doi[3] = 3;
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
#define SOL_IP 0
setsockopt(sockfd, SOL_IP, IP_OPTIONS,
&cipso, sizeof(struct cipso));
return 0;
}
CC: Lin Ming <mlin@xxxxxxxxxxxxx>
Reported-by: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Paul Moore <pmoore@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
net/ipv4/cipso_ipv4.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index d5ef60963183..f8f338874719 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -1727,8 +1727,10 @@ int cipso_v4_validate(const struct sk_buff *skb, unsigned char **option)
case CIPSO_V4_TAG_LOCAL:
/* This is a non-standard tag that we only allow for
* local connections, so if the incoming interface is
- * not the loopback device drop the packet. */
- if (!(skb->dev->flags & IFF_LOOPBACK)) {
+ * not the loopback device drop the packet. Further,
+ * there is no legitimate reason for setting this from
+ * userspace so reject it if skb is NULL. */
+ if (skb == NULL || !(skb->dev->flags & IFF_LOOPBACK)) {
err_offset = opt_iter;
goto validate_return_locked;
}
--
1.8.5.2
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