netdev - [PATCH] nfc: Ensure presence of required attributes in the activate

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Message-Id: <20170524104226.14841-1-mjurczyk@google.com>
Date:   Wed, 24 May 2017 12:42:26 +0200
From:   Mateusz Jurczyk <mjurczyk@...gle.com>
To:     Samuel Ortiz <sameo@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, security@...nel.org
Subject: [PATCH] nfc: Ensure presence of required attributes in the activate_target netlink handler

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 <mjurczyk@...gle.com>
---
 net/nfc/netlink.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
index 6b0850e63e09..b251fb936a27 100644
--- a/net/nfc/netlink.c
+++ b/net/nfc/netlink.c
@@ -907,7 +907,9 @@ static int nfc_genl_activate_target(struct sk_buff *skb, struct genl_info *info)
 	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]);
-- 
2.13.0.219.gdb65acc882-goog