netdev - Passing uninitialised local variable

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Date:   Wed, 28 Mar 2018 16:50:14 +0530
From:   Himanshu Jha <himanshujha199640@...il.com>
To:     arend.vanspriel@...adcom.com, franky.lin@...adcom.com,
        hante.meuleman@...adcom.com, chi-hsien.lin@...ress.com,
        wright.feng@...ress.com
Cc:     kvalo@...eaurora.org, johannes.berg@...el.com,
        linux-wireless@...r.kernel.org,
        brcm80211-dev-list.pdl@...adcom.com,
        brcm80211-dev-list@...ress.com, netdev@...r.kernel.org
Subject: Passing uninitialised local variable

Hello everyone,


I recently found that a local variable in passed uninitialised to the
function at 

drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c:2950

                u32 var; 
                err = brcmf_fil_iovar_int_get(ifp, "dtim_assoc", &var);
                if (err) {
                        brcmf_err("wl dtim_assoc failed (%d)\n", err);
                        goto update_bss_info_out;
                }
                dtim_period = (u8)var;


Now, the brcmf_fil_iovar_int_get() is defined as:

s32
brcmf_fil_iovar_int_get(struct brcmf_if *ifp, char *name, u32 *data)
{
        __le32 data_le = cpu_to_le32(*data);
        s32 err;

        err = brcmf_fil_iovar_data_get(ifp, name, &data_le, sizeof(data_le));
        if (err == 0)
                *data = le32_to_cpu(data_le);
        return err;
}

We can cleary see that 'var' in used uninitialised in the very first line
which is an undefined behavior.

So, what could be a possible fix for the above ?

I'm not sure initialising 'var' to 0 would be the correct solution.

-- 
Thanks
Himanshu Jha