netlink: Don't shift with UB on nlk->ngroups

[ Upstream commit 61f4b23769f0cc72ae62c9a81cf08f0397d40da8 ]

On i386 nlk->ngroups might be 32 or 0. Which leads to UB, resulting in
hang during boot.
Check for 0 ngroups and use (unsigned long long) as a type to shift.

Fixes: 7acf9d4237c4 ("netlink: Do not subscribe to non-existent groups").
Reported-by: kernel test robot <rong.a.chen@intel.com>
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>

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index cbcc92ebe97a2dec518f533dbb05b0ba3d299c28..26ff1c7bbcfa59e66f4c5fba70e1c9b5a467598b 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -985,7 +985,11 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr,
                if (err)
                        return err;
        }
-       groups &= (1UL << nlk->ngroups) - 1;
+
+       if (nlk->ngroups == 0)
+               groups = 0;
+       else
+               groups &= (1ULL << nlk->ngroups) - 1;
 
        bound = nlk->bound;
        if (bound) {