Messages in this thread | | | Date | Tue, 2 Mar 2021 09:31:23 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH] perf diff: Don't crash on freeing errno-session |
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Em Tue, Mar 02, 2021 at 01:47:55PM +0900, Namhyung Kim escreveu: > Hello, > > On Tue, Mar 2, 2021 at 11:35 AM Dmitry Safonov <dima@arista.com> wrote: > > > > __cmd_diff() sets result of perf_session__new() to d->session. > > In case of failure, it's errno and perf-diff may crash with: > > failed to open perf.data: Permission denied > > Failed to open perf.data > > Segmentation fault (core dumped) > > > > From the coredump: > > 0 0x00005569a62b5955 in auxtrace__free (session=0xffffffffffffffff) > > at util/auxtrace.c:2681 > > 1 0x00005569a626b37d in perf_session__delete (session=0xffffffffffffffff) > > at util/session.c:295 > > 2 perf_session__delete (session=0xffffffffffffffff) at util/session.c:291 > > 3 0x00005569a618008a in __cmd_diff () at builtin-diff.c:1239 > > 4 cmd_diff (argc=<optimized out>, argv=<optimized out>) at builtin-diff.c:2011 > > [..] > > > > Funny enough, it won't always crash. For me it crashes only if failed > > file is second in cmd-line: the reason is that cmd_diff() check files for > > branch-stacks [in check_file_brstack()] and if the first file doesn't > > have brstacks, it doesn't proceed to try open other files from cmd-line. > > > > Check d->session before calling perf_session__delete(). > > > > Another solution would be assigning to temporary variable, checking it, > > but I find it easier to follow with IS_ERR() check in the same function. > > After some time it's still obvious why the check is needed, and with > > temp variable it's possible to make the same mistake. > > > > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> > > Cc: Arnaldo Carvalho de Melo <acme@kernel.org> > > Cc: Ingo Molnar <mingo@redhat.com> > > Cc: Jiri Olsa <jolsa@redhat.com> > > Cc: Mark Rutland <mark.rutland@arm.com> > > Cc: Namhyung Kim <namhyung@kernel.org> > > Cc: Peter Zijlstra <peterz@infradead.org> > > Signed-off-by: Dmitry Safonov <dima@arista.com> > > Acked-by: Namhyung Kim <namhyung@kernel.org>
Thanks, tested, added a complete set of steps for a problem to be reproduced and applied.
- Arnaldo
Committer testing:
$ perf record sleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.001 MB perf.data (8 samples) ] $ perf diff failed to open perf.data.old: No such file or directory Failed to open perf.data.old $ perf record sleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.001 MB perf.data (8 samples) ] $ perf diff # Event 'cycles:u' # # Baseline Delta Abs Shared Object Symbol # ........ ......... ................ .......................... # 0.92% +87.66% [unknown] [k] 0xffffffff8825de16 11.39% +0.04% ld-2.32.so [.] __GI___tunables_init 87.70% ld-2.32.so [.] _dl_check_map_versions $ sudo chown root:root perf.data [sudo] password for acme: $ perf diff failed to open perf.data: Permission denied Failed to open perf.data Segmentation fault (core dumped) $ After the patch: $ perf diff failed to open perf.data: Permission denied Failed to open perf.data $ Signed-off-by: Dmitry Safonov <dima@arista.com> Acked-by: Namhyung Kim <namhyung@kernel.org> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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