linux-kernel - [PATCH 4.9 087/105] perf symbols: Robustify reading of build-id from sysfs

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Message-Id: <20170804231557.066300831@linuxfoundation.org>
Date:   Fri,  4 Aug 2017 16:15:55 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Markus Trippelsdorf <markus@...ppelsdorf.de>,
        Adrian Hunter <adrian.hunter@...el.com>,
        David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Wang Nan <wangnan0@...wei.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 087/105] perf symbols: Robustify reading of build-id from sysfs

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Arnaldo Carvalho de Melo <acme@...hat.com>


[ Upstream commit 7934c98a6e04028eb34c1293bfb5a6b0ab630b66 ]

Markus reported that perf segfaults when reading /sys/kernel/notes from
a kernel linked with GNU gold, due to what looks like a gold bug, so do
some bounds checking to avoid crashing in that case.

Reported-by: Markus Trippelsdorf <markus@...ppelsdorf.de>
Report-Link: http://lkml.kernel.org/r/20161219161821.GA294@x4
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Wang Nan <wangnan0@...wei.com>
Link: http://lkml.kernel.org/n/tip-ryhgs6a6jxvz207j2636w31c@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 tools/perf/util/symbol-elf.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -537,6 +537,12 @@ int sysfs__read_build_id(const char *fil
 				break;
 		} else {
 			int n = namesz + descsz;
+
+			if (n > (int)sizeof(bf)) {
+				n = sizeof(bf);
+				pr_debug("%s: truncating reading of build id in sysfs file %s: n_namesz=%u, n_descsz=%u.\n",
+					 __func__, filename, nhdr.n_namesz, nhdr.n_descsz);
+			}
 			if (read(fd, bf, n) != n)
 				break;
 		}