netlink: Don't shift on 64 for ngroups

It's legal to have 64 groups for netlink_sock.

As user-supplied nladdr->nl_groups is __u32, it's possible to subscribe
only to first 32 groups.

The check for correctness of .bind() userspace supplied parameter
is done by applying mask made from ngroups shift. Which broke Android
as they have 64 groups and the shift for mask resulted in an overflow.

Fixes: 61f4b23769f0 ("netlink: Don't shift with UB on nlk->ngroups")
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
Cc: stable@vger.kernel.org
Reported-and-Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index c09d16870f74a76bed23df737df7a134cf2bf310..56704d95f82d27f5a2bc26714e5001f3868765b2 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1013,8 +1013,8 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr,
 
        if (nlk->ngroups == 0)
                groups = 0;
-       else
-               groups &= (1ULL << nlk->ngroups) - 1;
+       else if (nlk->ngroups < 8*sizeof(groups))
+               groups &= (1UL << nlk->ngroups) - 1;
 
        bound = nlk->bound;
        if (bound) {