linux-kernel - Re: [PATCH v3] tools lib traceevent: add checks for returned EVENT

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Date:	Fri, 21 Aug 2015 00:57:55 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Dean Nelson <dnelson@...hat.com>
Cc:	a.p.zijlstra@...llo.org, mingo@...hat.com, rostedt@...dmis.org,
	acme@...nel.org, linux-kernel@...r.kernel.org, jolsa@...nel.org
Subject: Re: [PATCH v3] tools lib traceevent: add checks for returned
 EVENT_ERROR type

On Thu, Aug 20, 2015 at 11:16:32AM -0400, Dean Nelson wrote:
> Running the following perf-stat command on an arm64 system produces the
> following result...
> 
>   [root@...ch64 ~]# perf stat -e kmem:mm_page_alloc -a sleep 1
>     Warning: [kmem:mm_page_alloc] function sizeof not defined
>     Warning: Error: expected type 4 but read 0
>   Segmentation fault
>   [root@...ch64 ~]#
> 
> The second warning message and SIGSEGV stem from the issue expressed in the
> first warning message, and are the result of ignoring the EVENT_ERROR type
> returned back through the call chain.
> 
> Dealing with the first warning message is beyond the scope of this patch. But
> the second warning is addressed by this patch's first hunk. And the SIGSEGV is
> eliminated by its second hunk.
> 
> Signed-off-by: Dean Nelson <dnelson@...hat.com>

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thank you for fixing this!
Namhyung


> ---
> Changes in v3:
>   - The desire was that a goto be used, not what I'd done in v2.
> 
> Changes in v2:
>   - Moved the second hunk's check for EVENT_ERROR to a separate line.
> 
>  tools/lib/traceevent/event-parse.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
> index cc25f05..ed765a9 100644
> --- a/tools/lib/traceevent/event-parse.c
> +++ b/tools/lib/traceevent/event-parse.c
> @@ -1680,6 +1680,9 @@ process_cond(struct event_format *event, struct print_arg *top, char **tok)
>  	type = process_arg(event, left, &token);
>  
>   again:
> +	if (type == EVENT_ERROR)
> +		goto out_free;
> +
>  	/* Handle other operations in the arguments */
>  	if (type == EVENT_OP && strcmp(token, ":") != 0) {
>  		type = process_op(event, left, &token);
> @@ -1939,6 +1942,12 @@ process_op(struct event_format *event, struct print_arg *arg, char **tok)
>  			goto out_warn_free;
>  
>  		type = process_arg_token(event, right, tok, type);
> +		if (type == EVENT_ERROR) {
> +			free_arg(right);
> +			/* token was freed in process_arg_token() via *tok */
> +			token = NULL;
> +			goto out_free;
> +		}
>  
>  		if (right->type == PRINT_OP &&
>  		    get_op_prio(arg->op.op) < get_op_prio(right->op.op)) {
--
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