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perf machine: Guard against NULL in machine__exit()

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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: 33974a414c ("perf trace: Call machine__exit() at exit")
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2017-11-13 16:06:29 -03:00
parent 501e5bbec3
commit 4a2233b194
1 changed files with 3 additions and 0 deletions
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3
tools/perf/util/machine.c
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@ -172,6 +172,9 @@ void machine__exit(struct machine *machine)
{ {
int i; int i;
if (machine == NULL)
return;
machine__destroy_kernel_maps(machine); machine__destroy_kernel_maps(machine);
map_groups__exit(&machine->kmaps); map_groups__exit(&machine->kmaps);
dsos__exit(&machine->dsos); dsos__exit(&machine->dsos);