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SubjectRe: [PATCH 4.14] perf machine: Guard against NULL in machine__exit()
On Wed, Jun 19, 2019 at 12:00:46PM +0000, Rantala, Tommi T. (Nokia - FI/Espoo) wrote:
> 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(+)

Now applied, thanks.

greg k-h

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