netdev - Re: [PATCH net-next] wlcore: fix overlapping snprintf arguments in debugfs

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Date:   Sat, 17 Apr 2021 18:02:19 +0000 (UTC)
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Luciano Coelho <coelho@...com>, Arik Nemtsov <arik@...ery.com>,
        Arnd Bergmann <arnd@...db.de>,
        Lee Jones <lee.jones@...aro.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] wlcore: fix overlapping snprintf arguments in
 debugfs

Arnd Bergmann <arnd@...nel.org> wrote:

> From: Arnd Bergmann <arnd@...db.de>
> 
> gcc complains about undefined behavior in calling snprintf()
> with the same buffer as input and output:
> 
> drivers/net/wireless/ti/wl18xx/debugfs.c: In function 'diversity_num_of_packets_per_ant_read':
> drivers/net/wireless/ti/wl18xx/../wlcore/debugfs.h:86:3: error: 'snprintf' argument 4 overlaps destination object 'buf' [-Werror=restrict]
>    86 |   snprintf(buf, sizeof(buf), "%s[%d] = %d\n",  \
>       |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    87 |     buf, i, stats->sub.name[i]);   \
>       |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/wireless/ti/wl18xx/debugfs.c:24:2: note: in expansion of macro 'DEBUGFS_FWSTATS_FILE_ARRAY'
>    24 |  DEBUGFS_FWSTATS_FILE_ARRAY(a, b, c, wl18xx_acx_statistics)
>       |  ^~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/wireless/ti/wl18xx/debugfs.c:159:1: note: in expansion of macro 'WL18XX_DEBUGFS_FWSTATS_FILE_ARRAY'
>   159 | WL18XX_DEBUGFS_FWSTATS_FILE_ARRAY(diversity, num_of_packets_per_ant,
> 
> There are probably other ways of handling the debugfs file, without
> using on-stack buffers, but a simple workaround here is to remember the
> current position in the buffer and just keep printing in there.
> 
> Fixes: bcca1bbdd412 ("wlcore: add debugfs macro to help print fw statistics arrays")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Patch applied to wireless-drivers-next.git, thanks.

7b0e2c4f6be3 wlcore: fix overlapping snprintf arguments in debugfs

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20210323125723.1961432-1-arnd@kernel.org/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches