linux-kernel - Re: [PATCH v4] tracing: Replace deprecated strncpy() with strscpy() for stack_trace_filter

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Message-ID: <CA+RTe_gcBZh43txCyG6hQX5GF0bYbg8swJ5iPm4usanMn8BDAg@mail.gmail.com>
Date: Sat, 19 Apr 2025 14:59:25 +0530
From: Devaansh Kumar <devaanshk840@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: mhiramat@...nel.org, mathieu.desnoyers@...icios.com, 
	linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	skhan@...uxfoundation.org, linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH v4] tracing: Replace deprecated strncpy() with strscpy()
 for stack_trace_filter_buf

On Sat, 19 Apr 2025 at 08:15, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Sat, 19 Apr 2025 03:44:41 +0530
> Devaansh Kumar <devaanshk840@...il.com> wrote:
>
> > diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
> > index 14c6f272c4d8..0f2253f3bc8c 100644
> > --- a/kernel/trace/trace_stack.c
> > +++ b/kernel/trace/trace_stack.c
> > @@ -542,7 +542,7 @@ static __init int enable_stacktrace(char *str)
> >       int len;
> >
> >       if ((len = str_has_prefix(str, "_filter=")))
> > -             strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE);
> > +             strscpy(stack_trace_filter_buf, str + len, sizeof(stack_trace_filter_buf));
>
> Is the sizeof() needed?
>
> From include/linux/string.h:
>
> /**
>  * strscpy - Copy a C-string into a sized buffer
>  * @dst: Where to copy the string to
>  * @src: Where to copy the string from
>  * @...: Size of destination buffer (optional)
>  *
>  * Copy the source string @src, or as much of it as fits, into the
>  * destination @dst buffer. The behavior is undefined if the string
>  * buffers overlap. The destination @dst buffer is always NUL terminated,
>  * unless it's zero-sized.
>  *
>  * The size argument @... is only required when @dst is not an array, or
>  * when the copy needs to be smaller than sizeof(@dst).
>  *
>  * Preferred to strncpy() since it always returns a valid string, and
>  * doesn't unnecessarily force the tail of the destination buffer to be
>  * zero padded. If padding is desired please use strscpy_pad().
>  *
>  * Returns the number of characters copied in @dst (not including the
>  * trailing %NUL) or -E2BIG if @size is 0 or the copy from @src was
>  * truncated.
>  */
> #define strscpy(dst, src, ...)  \
>         CONCATENATE(__strscpy, COUNT_ARGS(__VA_ARGS__))(dst, src, __VA_ARGS__)
>
> With stack_trace_filter_buf defined as:
>
>   static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
>
> This looks like a text book example of just having that be:
>
>                 strscpy(stack_trace_filter_buf, str + len);
>

Right I have tested it, just using strscpy(stack_trace_filter_buf, str
+ len) works.


> -- Steve
>
>
> >
> >       stack_tracer_enabled = 1;
> >       return 1;