netdev - [PATCH 4.17 327/336] netlink: Do not subscribe to non-existent groups

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Message-Id: <20180801165041.552542865@linuxfoundation.org>
Date:   Wed,  1 Aug 2018 18:51:02 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        netdev@...r.kernel.org, Dmitry Safonov <dima@...sta.com>
Subject: [PATCH 4.17 327/336] netlink: Do not subscribe to non-existent groups

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

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

From: Dmitry Safonov <dima@...sta.com>

[ Upstream commit 7acf9d4237c46894e0fa0492dd96314a41742e84 ]

Make ABI more strict about subscribing to group > ngroups.
Code doesn't check for that and it looks bogus.
(one can subscribe to non-existing group)
Still, it's possible to bind() to all possible groups with (-1)

Cc: "David S. Miller" <davem@...emloft.net>
Cc: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@...unet.com>
Cc: netdev@...r.kernel.org
Signed-off-by: Dmitry Safonov <dima@...sta.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/netlink/af_netlink.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1008,6 +1008,7 @@ static int netlink_bind(struct socket *s
 		if (err)
 			return err;
 	}
+	groups &= (1UL << nlk->ngroups) - 1;
 
 	bound = nlk->bound;
 	if (bound) {