linux-kernel - Re: [PATCH] perf ftrace: Fix the buffer size in __write_tracing

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Message-ID: <20180108030512.begv5uoo66kh5biu@intel.com>
Date:   Mon, 8 Jan 2018 11:05:12 +0800
From:   "Du, Changbin" <changbin.du@...el.com>
To:     jolsa@...hat.com
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        changbin.du@...el.com
Subject: Re: [PATCH] perf ftrace: Fix the buffer size in __write_tracing_file

Hi Olsa,
What about this fix now? Thanks!

On Tue, Dec 26, 2017 at 05:26:56PM +0800, changbin.du@...el.com wrote:
> From: Changbin Du <changbin.du@...el.com>
> 
> The terminal character '\0' should take into account as size of the string
> buffer. Without this fix, the '--graph-funcs', '--nograph-funcs' and
> '--trace-funcs' options didn't work as expected when the <func> doesn't
> exist.
> 
> I didn't dive into kernel ftrace fops, but strace shows that if usersapce
> writes a non-terminated string, the kernel side will return success but
> no filter applied. After this fix in userspace, the kernel will return an
> error.
> 
> $ sudo ./perf ftrace -a --graph-depth 1 --graph-funcs abcdefg
>  0)   0.140 us    |  rcu_all_qs();
>  3)   0.304 us    |  mutex_unlock();
>  0)   0.153 us    |  find_vma();
>  3)   0.088 us    |  __fsnotify_parent();
>  0)   6.145 us    |  handle_mm_fault();
>  3)   0.089 us    |  fsnotify();
>  3)   0.161 us    |  __sb_end_write();
>  3)   0.710 us    |  SyS_close();
>  3)   7.848 us    |  exit_to_usermode_loop();
> 
> On above example, I specified function filter 'abcdefg' but all functions
> are enabled.
> 
> Signed-off-by: Changbin Du <changbin.du@...el.com>
> ---
>  tools/perf/builtin-ftrace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index 25a42ac..2604a64 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -69,7 +69,7 @@ static int __write_tracing_file(const char *name, const char *val, bool append)
>  {
>  	char *file;
>  	int fd, ret = -1;
> -	ssize_t size = strlen(val);
> +	ssize_t size = strlen(val) + 1;
>  	int flags = O_WRONLY;
>  	char errbuf[512];
>  
> -- 
> 2.7.4
> 

-- 
Thanks,
Changbin Du