The source code is 

static int ieee80211_set_mcast_rate(struct wiphy *wiphy, struct net_device *dev,
                    int rate[IEEE80211_NUM_BANDS])
{
    struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);

    memcpy(sdata->vif.bss_conf.mcast_rate, rate, sizeof(rate));

The compiler says

cfg.c: In function ‘int ieee80211_set_mcast_rate(wiphy*, net_device*, int*)’:
cfg.c:1995: warning: argument to ‘sizeof’ in ‘void* memcpy(void*, const void*, size_t)’ call is the same expression as the source; did you mean to dereference it? [-Wsizeof-pointer-memaccess]
     memcpy(rate2, rate, sizeof(rate));
                               ^

Here is static analyser cppcheck also finding the same problem

[linux-3.8-rc1/net/mac80211/cfg.c:1995]: (error) Using 'sizeof' on array given as function argument returns size of a pointer.


Suggest code rework.