Re: [PATCH 08/11] blktrace: convert strncpy() to strscpy_pad()

Steven Rostedt
2024-03-28T14:11:40Z

On Thu, 28 Mar 2024 15:04:52 +0100
Arnd Bergmann <arnd@kernel.org> wrote:

> From: Arnd Bergmann <arnd@arndb.de>
>
> gcc-9 warns about a possibly non-terminated string copy:
>
> kernel/trace/blktrace.c: In function 'do_blk_trace_setup':
> kernel/trace/blktrace.c:527:2: error: 'strncpy' specified bound 32 equals destination size [-Werror=stringop-truncation]
>
> Newer versions are fine here because they see the following explicit
> nul-termination. Using strscpy_pad() avoids the warning and
> simplifies the code a little. The padding helps give a clean
> buffer to userspace.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> kernel/trace/blktrace.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index d5d94510afd3..95a00160d465 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -524,8 +524,7 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
> if (!buts->buf_size || !buts->buf_nr)
> return -EINVAL;
>
> - strncpy(buts->name, name, BLKTRACE_BDEV_SIZE);
> - buts->name[BLKTRACE_BDEV_SIZE - 1] = '\0';
> + strscpy(buts->name, name, BLKTRACE_BDEV_SIZE);

The commit message says "Using strscpy_pad()" but it doesn't do so in the
patch.

Rule 12 of debugging: "When the comment and the code do not match, they are
probably both wrong"

-- Steve

>
> /*
> * some device names have larger paths - convert the slashes