linux-kernel - [PATCH -tip/urgent ] [BUGFIX] perf/probe: Fix a segfault if asked for variable it doesn't find

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Date:	Thu, 29 May 2014 19:52:32 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: [PATCH -tip/urgent ] [BUGFIX] perf/probe: Fix a segfault if asked
 for variable it doesn't find

Fix a segfault bug by asking for variable it doesn't find.
Since the convert_variable() didn't handle error code returned
from convert_variable_location(), it just passed an incomplete
variable field and then a segfault was occured when formatting
the field.

This fixes that bug by handling success code correctly in
convert_variable(). Other callers of convert_variable_location()
are correctly checking the return code.

This bug was introduced by following commit. But another hidden
erroneous error handling has been there previuosly (-ENOMEM case).

 commit 3d918a12a1b3088ac16ff37fa52760639d6e2403

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Reported-by: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Jiri Olsa <jolsa@...hat.com>
---
 tools/perf/util/probe-finder.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 5627621..9d8eb26 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -511,12 +511,12 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
 
 	ret = convert_variable_location(vr_die, pf->addr, pf->fb_ops,
 					&pf->sp_die, pf->tvar);
-	if (ret == -ENOENT)
+	if (ret == -ENOENT || ret == -EINVAL)
 		pr_err("Failed to find the location of %s at this address.\n"
 		       " Perhaps, it has been optimized out.\n", pf->pvar->var);
 	else if (ret == -ENOTSUP)
 		pr_err("Sorry, we don't support this variable location yet.\n");
-	else if (pf->pvar->field) {
+	else if (ret == 0 && pf->pvar->field) {
 		ret = convert_variable_fields(vr_die, pf->pvar->var,
 					      pf->pvar->field, &pf->tvar->ref,
 					      &die_mem);


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