2019-06-19 12:01:12

by Tommi Rantala

Subject: [PATCH 4.14] perf machine: Guard against NULL in machine__exit()

From: Arnaldo Carvalho de Melo <[email protected]>

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 <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andrei Vagin <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Vasily Averin <[email protected]>
Cc: Wang Nan <[email protected]>
Fixes: 33974a414ce2 ("perf trace: Call machine__exit() at exit")
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
Signed-off-by: Tommi Rantala <[email protected]>
---
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

2019-06-19 12:32:30

by Greg Kroah-Hartman

Subject: Re: [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 <[email protected]>
>
> 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 <[email protected]>
> Cc: Alexander Shishkin <[email protected]>
> Cc: Andrei Vagin <[email protected]>
> Cc: David Ahern <[email protected]>
> Cc: Jiri Olsa <[email protected]>
> Cc: Namhyung Kim <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Vasily Averin <[email protected]>
> Cc: Wang Nan <[email protected]>
> Fixes: 33974a414ce2 ("perf trace: Call machine__exit() at exit")
> Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
> Signed-off-by: Tommi Rantala <[email protected]>
> ---
> tools/perf/util/machine.c | 3 +++
> 1 file changed, 3 insertions(+)

Now applied, thanks.

greg k-h