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

From: Greg Kroah-Hartman
Date: Fri Aug 04 2017 - 19:18:35 EST

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


From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

[ 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@xxxxxxxxxxxxxxx>
Report-Link: http://lkml.kernel.org/r/20161219161821.GA294@x4
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-ryhgs6a6jxvz207j2636w31c@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
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
} 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)