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Date:   Fri, 10 Apr 2020 13:38:15 -0700
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     Marco Elver <elver@google.com>
Cc:     kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] kcsan: Fix function matching in report
Message-ID: <20200410203815.GV17661@paulmck-ThinkPad-P72>
Reply-To: paulmck@kernel.org
References: <20200410164418.65808-1-elver@google.com>
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On Fri, Apr 10, 2020 at 06:44:17PM +0200, Marco Elver wrote:
> Pass string length as returned by scnprintf() to strnstr(), since
> strnstr() searches exactly len bytes in haystack, even if it contains a
> NUL-terminator before haystack+len.
> 
> Signed-off-by: Marco Elver <elver@google.com>

I queued both for testing and review, thank you, Marco!

							Thanx, Paul

> ---
>  kernel/kcsan/report.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c
> index ddc18f1224a4..cf41d63dd0cd 100644
> --- a/kernel/kcsan/report.c
> +++ b/kernel/kcsan/report.c
> @@ -192,11 +192,11 @@ skip_report(enum kcsan_value_change value_change, unsigned long top_frame)
>  		 * maintainers.
>  		 */
>  		char buf[64];
> +		int len = scnprintf(buf, sizeof(buf), "%ps", (void *)top_frame);
>  
> -		snprintf(buf, sizeof(buf), "%ps", (void *)top_frame);
> -		if (!strnstr(buf, "rcu_", sizeof(buf)) &&
> -		    !strnstr(buf, "_rcu", sizeof(buf)) &&
> -		    !strnstr(buf, "_srcu", sizeof(buf)))
> +		if (!strnstr(buf, "rcu_", len) &&
> +		    !strnstr(buf, "_rcu", len) &&
> +		    !strnstr(buf, "_srcu", len))
>  			return true;
>  	}
>  
> @@ -262,15 +262,15 @@ static const char *get_thread_desc(int task_id)
>  static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries)
>  {
>  	char buf[64];
> +	int len;
>  	int skip = 0;
>  
>  	for (; skip < num_entries; ++skip) {
> -		snprintf(buf, sizeof(buf), "%ps", (void *)stack_entries[skip]);
> -		if (!strnstr(buf, "csan_", sizeof(buf)) &&
> -		    !strnstr(buf, "tsan_", sizeof(buf)) &&
> -		    !strnstr(buf, "_once_size", sizeof(buf))) {
> +		len = scnprintf(buf, sizeof(buf), "%ps", (void *)stack_entries[skip]);
> +		if (!strnstr(buf, "csan_", len) &&
> +		    !strnstr(buf, "tsan_", len) &&
> +		    !strnstr(buf, "_once_size", len))
>  			break;
> -		}
>  	}
>  	return skip;
>  }
> -- 
> 2.26.0.110.g2183baf09c-goog
>