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Subject[PATCH 4.14] perf machine: Guard against NULL in machine__exit()
Date
From: Arnaldo Carvalho de Melo <acme@redhat.com>

commit 4a2233b194c77ae1ea8304cb7c00b551de4313f0 upstream.

A recent fix for 'perf trace' introduced a bug where
machine__exit(trace->host) could be called while trace->host was still
NULL, so make this more robust by guarding against NULL, just like
free() does.

The problem happens, for instance, when !root users try to run 'perf
trace':

[acme@jouet linux]$ trace
Error: No permissions to read /sys/kernel/debug/tracing/events/raw_syscalls/sys_(enter|exit)
Hint: Try 'sudo mount -o remount,mode=755 /sys/kernel/debug/tracing'

perf: Segmentation fault
Obtained 7 stack frames.
[0x4f1b2e]
/lib64/libc.so.6(+0x3671f) [0x7f43a1dd971f]
[0x4f3fec]
[0x47468b]
[0x42a2db]
/lib64/libc.so.6(__libc_start_main+0xe9) [0x7f43a1dc3509]
[0x42a6c9]
Segmentation fault (core dumped)
[acme@jouet linux]$

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrei Vagin <avagin@openvz.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vasily Averin <vvs@virtuozzo.com>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: 33974a414ce2 ("perf trace: Call machine__exit() at exit")
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
---
tools/perf/util/machine.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 968fd0454e6b..d246080cd85e 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -156,6 +156,9 @@ void machine__delete_threads(struct machine *machine)

void machine__exit(struct machine *machine)
{
+ if (machine == NULL)
+ return;
+
machine__destroy_kernel_maps(machine);
map_groups__exit(&machine->kmaps);
dsos__exit(&machine->dsos);
--
2.20.1
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