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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Steffen Klassert <steffen.klassert@secunet.com>,
        netdev@vger.kernel.org, Dmitry Safonov <dima@arista.com>
Subject: [PATCH 4.4 106/124] netlink: Do not subscribe to non-existent groups
Date:   Sat,  4 Aug 2018 11:01:35 +0200
Message-Id: <20180804082706.427556290@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Dmitry Safonov <dima@arista.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@davemloft.net>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/netlink/af_netlink.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -983,6 +983,7 @@ static int netlink_bind(struct socket *s
 		if (err)
 			return err;
 	}
+	groups &= (1UL << nlk->ngroups) - 1;
 
 	bound = nlk->bound;
 	if (bound) {