wl12xx: fix potential buffer overflow in testmode nvs push

wl12xx: fix potential buffer overflow in testmode nvs push

commit 09b661b33268698d3b453dceb78cda129ad899b4 upstream.

We were allocating the size of the NVS file struct and not checking
whether the length of the buffer passed was correct before copying it
into the allocated memory.  This is a security hole because buffer
overflows can occur if the userspace passes a bigger file than what is
expected.

With this patch, we check if the size of the data passed from
userspace matches the size required.

This bug was introduced in 2.6.36.

Reported-by: Ido Yariv <ido@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>