netlink: Fix spectre v1 gadget in netlink_create()
'protocol' is a user-controlled value, so sanitize it after the bounds
check to avoid using it for speculative out-of-bounds access to arrays
indexed by it.
This addresses the following accesses detected with the help of smatch:
* net/netlink/af_netlink.c:654 __netlink_create() warn: potential
spectre issue 'nlk_cb_mutex_keys' [w]
* net/netlink/af_netlink.c:654 __netlink_create() warn: potential
spectre issue 'nlk_cb_mutex_key_strings' [w]
* net/netlink/af_netlink.c:685 netlink_create() warn: potential spectre
issue 'nl_table' [w] (local cap)
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jeremy Cline <jcline@redhat.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>