strncpy() is deprecated for NUL-terminated destination buffers and must
be replaced by strscpy().

See issue: https://github.com/KSPP/linux/issues/90

Signed-off-by: Devaansh Kumar <devaanshk840@gmail.com>
---
 kernel/trace/trace_stack.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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));
 
 	stack_tracer_enabled = 1;
 	return 1;
-- 
2.49.0

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);

-- Steve


>  
>  	stack_tracer_enabled = 1;
>  	return 1;

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;