linux-kernel - Re: [PATCH 09/22] net: niu: fix format string overflow warning:

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Message-Id: <20170714.090340.81439675812003295.davem@davemloft.net>
Date:   Fri, 14 Jul 2017 09:03:40 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     arnd@...db.de
Cc:     linux-kernel@...r.kernel.org, tremyfr@...il.com,
        gregkh@...uxfoundation.org, torvalds@...ux-foundation.org,
        linux@...ck-us.net, akpm@...ux-foundation.org,
        netdev@...r.kernel.org, jejb@...ux.vnet.ibm.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        x86@...nel.org, edumazet@...gle.com, stephen@...workplumber.org,
        jarod@...hat.com
Subject: Re: [PATCH 09/22] net: niu: fix format string overflow warning:

From: Arnd Bergmann <arnd@...db.de>
Date: Fri, 14 Jul 2017 14:07:01 +0200

> We get a warning for the port_name string that might be longer than
> six characters if we had more than 10 ports:
> 
> drivers/net/ethernet/sun/niu.c: In function 'niu_put_parent':
> drivers/net/ethernet/sun/niu.c:9563:21: error: '%d' directive writing between 1 and 3 bytes into a region of size 2 [-Werror=format-overflow=]
>   sprintf(port_name, "port%d", port);
>                      ^~~~~~~~
> drivers/net/ethernet/sun/niu.c:9563:21: note: directive argument in the range [0, 255]
> drivers/net/ethernet/sun/niu.c:9563:2: note: 'sprintf' output between 6 and 8 bytes into a destination of size 6
>   sprintf(port_name, "port%d", port);
>   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/sun/niu.c: In function 'niu_pci_init_one':
> drivers/net/ethernet/sun/niu.c:9538:22: error: '%d' directive writing between 1 and 3 bytes into a region of size 2 [-Werror=format-overflow=]
>    sprintf(port_name, "port%d", port);
>                       ^~~~~~~~
> drivers/net/ethernet/sun/niu.c:9538:22: note: directive argument in the range [0, 255]
> drivers/net/ethernet/sun/niu.c:9538:3: note: 'sprintf' output between 6 and 8 bytes into a destination of size 6
> 
> While we know that the port number is small, there is no harm in
> making the format string two bytes longer to avoid the warning.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Applied.