linux-kernel - Re: [PATCH] ath10k: work around uninitialized vht

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Date:   Mon, 8 Jul 2019 07:46:38 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Kalle Valo <kvalo@...eaurora.org>,
        Miaoqing Pan <miaoqing@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rakesh Pillai <pillair@...eaurora.org>,
        Brian Norris <briannorris@...omium.org>,
        Balaji Pothunoori <bpothuno@...eaurora.org>,
        Wen Gong <wgong@...eaurora.org>,
        Pradeep kumar Chitrapu <pradeepc@...eaurora.org>,
        Sriram R <srirrama@...eaurora.org>, ath10k@...ts.infradead.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] ath10k: work around uninitialized vht_pfr variable

On Mon, Jul 08, 2019 at 02:50:06PM +0200, Arnd Bergmann wrote:
> As clang points out, the vht_pfr is assigned to a struct member
> without being initialized in one case:
> 
> drivers/net/wireless/ath/ath10k/mac.c:7528:7: error: variable 'vht_pfr' is used uninitialized whenever 'if' condition
>       is false [-Werror,-Wsometimes-uninitialized]
>                 if (!ath10k_mac_can_set_bitrate_mask(ar, band, mask,
>                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/wireless/ath/ath10k/mac.c:7551:20: note: uninitialized use occurs here
>                 arvif->vht_pfr = vht_pfr;
>                                  ^~~~~~~
> drivers/net/wireless/ath/ath10k/mac.c:7528:3: note: remove the 'if' if its condition is always true
>                 if (!ath10k_mac_can_set_bitrate_mask(ar, band, mask,
>                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/wireless/ath/ath10k/mac.c:7483:12: note: initialize the variable 'vht_pfr' to silence this warning
>         u8 vht_pfr;
> 
> Add an explicit but probably incorrect initialization here.
> I suspect we want a better fix here, but chose this approach to
> illustrate the issue.

Yup, I reached out to the maintainers when this issue first cropped up,
should have taken your approach though.

https://lore.kernel.org/lkml/20190702181837.GA118849@archlinux-epyc/

Initializing to zero is better than uninitialized.

> 
> Fixes: 8b97b055dc9d ("ath10k: fix failure to set multiple fixed rate")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Nathan Chancellor <natechancellor@...il.com>