linux-kernel - [tip:perf/urgent] perf symbols: Robustify reading of build-id from sysfs

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Message-ID: <tip-ryhgs6a6jxvz207j2636w31c@git.kernel.org>
Date:   Wed, 4 Jan 2017 23:53:37 -0800
From:   tip-bot for Arnaldo Carvalho de Melo <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     adrian.hunter@...el.com, wangnan0@...wei.com, acme@...hat.com,
        jolsa@...nel.org, mingo@...nel.org, namhyung@...nel.org,
        dsahern@...il.com, hpa@...or.com, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, markus@...ppelsdorf.de
Subject: [tip:perf/urgent] perf symbols: Robustify reading of build-id from
 sysfs

Commit-ID:  7934c98a6e04028eb34c1293bfb5a6b0ab630b66
Gitweb:     http://git.kernel.org/tip/7934c98a6e04028eb34c1293bfb5a6b0ab630b66
Author:     Arnaldo Carvalho de Melo <acme@...hat.com>
AuthorDate: Tue, 3 Jan 2017 15:19:21 -0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Tue, 3 Jan 2017 16:11:13 -0300

perf symbols: Robustify reading of build-id from sysfs

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>
---
 tools/perf/util/symbol-elf.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 99400b0..adbc6c0 100644
--- 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 *filename, void *build_id, size_t size)
 				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;
 		}