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

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

From: Mateusz Jurczyk <redacted>

commit a0323b979f81ad2deb2c8836eab506534891876a upstream.

Check that the NFC_ATTR_TARGET_INDEX and NFC_ATTR_PROTOCOLS attributes (in
addition to NFC_ATTR_DEVICE_INDEX) are provided by the netlink client
prior to accessing them. This prevents potential unhandled NULL pointer
dereference exceptions which can be triggered by malicious user-mode
programs, if they omit one or both of these attributes.

Signed-off-by: Mateusz Jurczyk <redacted>
Acked-by: Kees Cook <redacted>
Signed-off-by: Samuel Ortiz <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/nfc/netlink.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/nfc/netlink.c
+++ b/net/nfc/netlink.c

@@ -907,7 +907,9 @@ static int nfc_genl_activate_target(stru
 	u32 device_idx, target_idx, protocol;
 	int rc;
 
-	if (!info->attrs[NFC_ATTR_DEVICE_INDEX])
+	if (!info->attrs[NFC_ATTR_DEVICE_INDEX] ||
+	    !info->attrs[NFC_ATTR_TARGET_INDEX] ||
+	    !info->attrs[NFC_ATTR_PROTOCOLS])
 		return -EINVAL;
 
 	device_idx = nla_get_u32(info->attrs[NFC_ATTR_DEVICE_INDEX]);