Re: [PATCH v4] tracing: Replace deprecated strncpy() with strscpy() for stack_trace_filter_buf

Devaansh Kumar
2025-04-19T09:29:39Z

On Sat, 19 Apr 2025 at 08:15, Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Sat, 19 Apr 2025 03:44:41 +0530
> Devaansh Kumar <devaanshk840@gmail.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;