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    Subject[PATCH 3.16 305/366] netlink: Don't shift with UB on nlk->ngroups
    3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

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

    From: Dmitry Safonov <dima@arista.com>

    commit 61f4b23769f0cc72ae62c9a81cf08f0397d40da8 upstream.

    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: Ben Hutchings <ben@decadent.org.uk>
    ---
    net/netlink/af_netlink.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    --- a/net/netlink/af_netlink.c
    +++ b/net/netlink/af_netlink.c
    @@ -927,7 +927,11 @@ static int netlink_bind(struct socket *s
    if (err)
    return err;
    }
    - groups &= (1UL << nlk->ngroups) - 1;
    +
    + if (nlk->ngroups == 0)
    + groups = 0;
    + else
    + groups &= (1ULL << nlk->ngroups) - 1;

    if (nlk->portid)
    if (nladdr->nl_pid != nlk->portid)
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