net: 4 bytes kernel memory disclosure in SO_BSDCOMPAT gsopt try #2

[ Upstream commit df0bca049d01c0ee94afb7cd5dfd959541e6c8da ]

In function sock_getsockopt() located in net/core/sock.c, optval v.val
is not correctly initialized and directly returned in userland in case
we have SO_BSDCOMPAT option set.

This dummy code should trigger the bug:

int main(void)
{
	unsigned char buf[4] = { 0, 0, 0, 0 };
	int len;
	int sock;
	sock = socket(33, 2, 2);
	getsockopt(sock, 1, SO_BSDCOMPAT, &buf, &len);
	printf("%x%x%x%x\n", buf[0], buf[1], buf[2], buf[3]);
	close(sock);
}

Here is a patch that fix this bug by initalizing v.val just after its
declaration.

Signed-off-by: Clément Lecigne <clement.lecigne@netasq.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/core/sock.c b/net/core/sock.c
index edf7220889a4b75f1e1671c39aeef8c31351387b..a7a09758c62db9b153eab88bdd4624a9f5c24290 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -696,6 +696,8 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
        if (len < 0)
                return -EINVAL;
 
+       v.val = 0;
+
        switch(optname) {
        case SO_DEBUG:
                v.val = sock_flag(sk, SOCK_DBG);