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

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Message-ID: <20151120014622.GE23310@sejong>
Date:	Fri, 20 Nov 2015 10:46:22 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>
CC:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	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>, Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH perf/core 01/13] perf probe: Fix to free temporal
 Dwarf_Frame

Hi Masami,

On Thu, Nov 19, 2015 at 03:12:37AM +0000, 平松雅巳 / HIRAMATU，MASAMI wrote:
> 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

Ah, missed that.  Thank you.
Namhyung


> 
> >>>  		}
> >>> +		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.
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