Re: [PATCH] tools lib api fs: fix gcc9 compilation error

[Jiri Olsa]

On Wed, Dec 11, 2019 at 08:01:09AM +0000, Andrey Zhizhikin wrote:
> GCC9 introduced string hardening mechanisms, which exhibits the error
> during fs api compilation:
> 
> error: '__builtin_strncpy' specified bound 4096 equals destination size
> [-Werror=stringop-truncation]
> 
> This comes when the length of copy passed to strncpy is is equal to
> destination size, which could potentially lead to buffer overflow.
> 
> There is a need to mitigate this potential issue by limiting the size of
> destination by 1 and explicitly terminate the destination with NULL.
> 
> Signed-off-by: Andrey Zhizhikin <andrey.zhizhikin@xxxxxxxxxxxxxxxxxxxx>
> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>

Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>

thanks,
jirka

> ---
>  tools/lib/api/fs/fs.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
> index 11b3885e833e..027b18f7ed8c 100644
> --- a/tools/lib/api/fs/fs.c
> +++ b/tools/lib/api/fs/fs.c
> @@ -210,6 +210,7 @@ static bool fs__env_override(struct fs *fs)
>  	size_t name_len = strlen(fs->name);
>  	/* name + "_PATH" + '\0' */
>  	char upper_name[name_len + 5 + 1];
> +
>  	memcpy(upper_name, fs->name, name_len);
>  	mem_toupper(upper_name, name_len);
>  	strcpy(&upper_name[name_len], "_PATH");
> @@ -219,7 +220,8 @@ static bool fs__env_override(struct fs *fs)
>  		return false;
>  
>  	fs->found = true;
> -	strncpy(fs->path, override_path, sizeof(fs->path));
> +	strncpy(fs->path, override_path, sizeof(fs->path) - 1);
> +	fs->path[sizeof(fs->path) - 1] = '\0';
>  	return true;
>  }
>  
> -- 
> 2.17.1
>