linux-kernel - Re: [PATCH] btrfs: use correct string length

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Date:   Tue, 9 Jan 2018 18:36:20 +0100
From:   David Sterba <dsterba@...e.cz>
To:     Xiongfeng Wang <wangxiongfeng2@...wei.com>
Cc:     dsterba@...e.com, clm@...com, jbacik@...com,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        arnd@...db.de
Subject: Re: [PATCH] btrfs: use correct string length

On Mon, Jan 08, 2018 at 07:51:22PM +0800, Xiongfeng Wang wrote:
> From: Xiongfeng Wang <xiongfeng.wang@...aro.org>
> 
> gcc-8 reports
> 
> fs/btrfs/ioctl.c: In function 'btrfs_ioctl':
> ./include/linux/string.h:245:9: warning: '__builtin_strncpy' specified
> bound 1024 equals destination size [-Wstringop-truncation]
> 
> We need one less byte or call strlcpy() to make it a nul-terminated
> string.

The null termination is on the following line, so this patch fixes
namely the gcc warning:

> -		strncpy(di_args->path, name->str, sizeof(di_args->path));
> +		strncpy(di_args->path, name->str, sizeof(di_args->path) - 1);
>  		rcu_read_unlock();
>  		di_args->path[sizeof(di_args->path) - 1] = 0;

Reviewed-by: David Sterba <dsterba@...e.com>