Re: [PATCH v2] tracing/probe: reject empty immediate strings

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Thu,  2 Apr 2026 00:03:15 +0800
Pengpeng Hou <pengpeng@iscas.ac.cn> wrote:

> parse_probe_arg() accepts quoted immediate strings and passes the body
> after the opening quote to __parse_imm_string(). That helper currently
> computes strlen(str) and immediately dereferences str[len - 1], which
> underflows when the body is empty.
> 
> Reject empty immediate strings before checking for the closing quote.
> 

Oops, good catch!

Let me pick it.

Thank you!

> Fixes: a42e3c4de964 ("tracing/probe: Add immediate string parameter support")
> Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
> ---
> Changes since v1:
> - resend as a standalone patch instead of part of an accidental
>   cross-subsystem 1/4 series
> 
>  kernel/trace/trace_probe.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index e0a5dc86c07e..e1c73065dae5 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -1068,7 +1068,7 @@ static int __parse_imm_string(char *str, char **pbuf, int offs)
>  {
>  	size_t len = strlen(str);
>  
> -	if (str[len - 1] != '"') {
> +	if (!len || str[len - 1] != '"') {
>  		trace_probe_log_err(offs + len, IMMSTR_NO_CLOSE);
>  		return -EINVAL;
>  	}
> -- 
> 2.50.1 (Apple Git-155)
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>