linux-kernel - RE: [PATCH perf/core 01/13] perf probe: Fix to free temporal Dwarf

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Date:	Thu, 19 Nov 2015 03:12:37 +0000
From:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>
To:	"'Namhyung Kim'" <namhyung@...il.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Ingo Molnar" <mingo@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>
Subject: RE: [PATCH perf/core 01/13] perf probe: Fix to free temporal
 Dwarf_Frame

From: Namhyung Kim [mailto:namhyung@...il.com]
>On November 19, 2015 7:36:39 AM GMT+09:00, Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
>>Em Wed, Nov 18, 2015 at 03:40:12PM +0900, Masami Hiramatsu escreveu:
>>> Since dwarf_cfi_addrframe returns malloc'd Dwarf_Frame
>>> object, it has to be freed after used.
>>
>>Applied to perf/urgent
>>
>>> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
>>> ---
>>>  tools/perf/util/probe-finder.c |    9 ++++++---
>>>  1 file changed, 6 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/tools/perf/util/probe-finder.c
>>b/tools/perf/util/probe-finder.c
>>> index 63993d7..4d7d4f4 100644
>>> --- a/tools/perf/util/probe-finder.c
>>> +++ b/tools/perf/util/probe-finder.c
>>> @@ -683,21 +683,24 @@ static int call_probe_finder(Dwarf_Die *sc_die,
>>struct probe_finder *pf)
>>>  	ret = dwarf_getlocation_addr(&fb_attr, pf->addr, &pf->fb_ops,
>>&nops, 1);
>>>  	if (ret <= 0 || nops == 0) {
>>>  		pf->fb_ops = NULL;
>>> +		ret = 0;
>>>  #if _ELFUTILS_PREREQ(0, 142)
>>>  	} else if (nops == 1 && pf->fb_ops[0].atom == DW_OP_call_frame_cfa
>>&&
>>>  		   pf->cfi != NULL) {
>>> -		Dwarf_Frame *frame;
>>> +		Dwarf_Frame *frame = NULL;
>>>  		if (dwarf_cfi_addrframe(pf->cfi, pf->addr, &frame) != 0 ||
>>>  		    dwarf_frame_cfa(frame, &pf->fb_ops, &nops) != 0) {
>
>What if dwarf_cfi_addrframe() succeeded but
>dwarf_frame_cfa() failed?  It seems that the frame
>still can be leaked..

No, it is also caught by free(). Please see below,
>
>>>  			pr_warning("Failed to get call frame on 0x%jx\n",
>>>  				   (uintmax_t)pf->addr);
>>> -			return -ENOENT;
>>> +			ret = -ENOENT;

I've replaced "return -ENOENT" with "ret = -ENOENT", so this fall down

>>>  		}
>>> +		free(frame);

and free the frame :) (and if frame == NULL, it is just ignored)

Thank you!


>>>  #endif
>>>  	}
>>>
>>>  	/* Call finder's callback handler */
>>> -	ret = pf->callback(sc_die, pf);
>>> +	if (ret >= 0)
>>> +		ret = pf->callback(sc_die, pf);
>>>
>>>  	/* *pf->fb_ops will be cached in libdw. Don't free it. */
>>>  	pf->fb_ops = NULL;
>
>Hi Arnaldo and Masami,
>--
>Sent from my Android device with K-9 Mail. Please excuse my brevity.