netdev - Re: [PATCH] wireless: fix bogus maybe-uninitialized warning

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87mvh9qwhi.fsf@purkki.adurom.net>
Date:   Wed, 09 Nov 2016 03:21:13 +0200
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Arnd Bergmann <arnd@...db.de>,
        Johannes Berg <johannes@...solutions.net>
Cc:     Stanislav Yakovlev <stas.yakovlev@...il.com>,
        Jouni Malinen <j@...fi>,
        "David S. Miller" <davem@...emloft.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] wireless: fix bogus maybe-uninitialized warning

Arnd Bergmann <arnd@...db.de> writes:

> The hostap_80211_rx() function is supposed to set up the mac addresses
> for four possible cases, based on two bits of input data. For
> some reason, gcc decides that it's possible that none of the these
> four cases apply and the addresses remain uninitialized:
>
> drivers/net/wireless/intersil/hostap/hostap_80211_rx.c: In function ‘hostap_80211_rx’:
> arch/x86/include/asm/string_32.h:77:14: warning: ‘src’ may be used uninitialized in this function [-Wmaybe-uninitialized]
> drivers/net/wireless/intel/ipw2x00/libipw_rx.c: In function ‘libipw_rx’:
> arch/x86/include/asm/string_32.h:77:14: error: ‘dst’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> arch/x86/include/asm/string_32.h:78:22: error: ‘*((void *)&dst+4)’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>
> This warning is clearly nonsense, but changing the last case into
> 'default' makes it obvious to the compiler too, which avoids the
> warning and probably leads to better object code too.
>
> The same code is duplicated several times in the kernel, so this
> patch uses the same workaround for all copies. The exact configuration
> was hit only very rarely in randconfig builds and I only saw it
> in three drivers, but I assume that all of them are potentially
> affected, and it's better to keep the code consistent.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/net/wireless/ath/ath6kl/wmi.c                  | 8 ++++----
>  drivers/net/wireless/intel/ipw2x00/libipw_rx.c         | 2 +-
>  drivers/net/wireless/intersil/hostap/hostap_80211_rx.c | 2 +-
>  net/wireless/lib80211_crypt_tkip.c                     | 2 +-
>  4 files changed, 7 insertions(+), 7 deletions(-)

[...]

> --- a/net/wireless/lib80211_crypt_tkip.c
> +++ b/net/wireless/lib80211_crypt_tkip.c
> @@ -556,7 +556,7 @@ static void michael_mic_hdr(struct sk_buff *skb, u8 * hdr)
>  		memcpy(hdr, hdr11->addr3, ETH_ALEN);	/* DA */
>  		memcpy(hdr + ETH_ALEN, hdr11->addr4, ETH_ALEN);	/* SA */
>  		break;
> -	case 0:
> +	default:
>  		memcpy(hdr, hdr11->addr1, ETH_ALEN);	/* DA */
>  		memcpy(hdr + ETH_ALEN, hdr11->addr2, ETH_ALEN);	/* SA */
>  		break;

Ideally we prefer that drivers/net/wireless and net/wireless changes are
split into different patches as they get applied to different trees.
Johannes, is it ok if I take this change through my tree this time?

-- 
Kalle Valo