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SubjectRe: [PATCH] perf map: Fix namespace memory leak
Hi,

As with:
https://lore.kernel.org/linux-perf-users/20220122045811.3402706-4-irogers@google.com/
I implemented REFCNT_CHECKING for nsinfo (I'll mail it soon). This
more accurately identifies the problem. In one run I got:
```
=================================================================
==3900722==ERROR: AddressSanitizer: attempting double-free on
0x602000026710 in thread T6:
#0 0x7f9a1dd6f4d7 in __interceptor_free
../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:127
#1 0x5650d04cb29c in nsinfo__put util/namespaces.c:259
#2 0x5650d04aba93 in map__new util/map.c:198
#3 0x5650d04a11f6 in machine__process_mmap2_event util/machine.c:1798
#4 0x5650d04a24bf in machine__process_event util/machine.c:2019
#5 0x5650d03e78b3 in perf_event__process util/event.c:567
#6 0x5650d056e3bb in perf_tool__process_synth_event
util/synthetic-events.c:65
#7 0x5650d05711a6 in perf_event__synthesize_mmap_events
util/synthetic-events.c:501
#8 0x5650d0572fc0 in __event__synthesize_thread util/synthetic-events.c:792
#9 0x5650d05739fd in __perf_event__synthesize_threads
util/synthetic-events.c:929
#10 0x5650d0573cbd in synthesize_threads_worker util/synthetic-events.c:961
#11 0x7f9a1dc48d7f in start_thread nptl/pthread_create.c:481
#12 0x7f9a1cfdcb6e in clone (/lib/x86_64-linux-gnu/libc.so.6+0xfcb6e)

0x602000026710 is located 0 bytes inside of 8-byte region
[0x602000026710,0x602000026718)
freed by thread T13 here:
#0 0x7f9a1dd6f4d7 in __interceptor_free
../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:127
#1 0x5650d04cb29c in nsinfo__put util/namespaces.c:259
#2 0x5650d04aba93 in map__new util/map.c:198
#3 0x5650d04a11f6 in machine__process_mmap2_event util/machine.c:1798
#4 0x5650d04a24bf in machine__process_event util/machine.c:2019
#5 0x5650d03e78b3 in perf_event__process util/event.c:567
#6 0x5650d056e3bb in perf_tool__process_synth_event
util/synthetic-events.c:65
#7 0x5650d05711a6 in perf_event__synthesize_mmap_events
util/synthetic-events.c:501
#8 0x5650d0572fc0 in __event__synthesize_thread util/synthetic-events.c:792
#9 0x5650d05739fd in __perf_event__synthesize_threads
util/synthetic-events.c:929
#10 0x5650d0573cbd in synthesize_threads_worker util/synthetic-events.c:961
#11 0x7f9a1dc48d7f in start_thread nptl/pthread_create.c:481

previously allocated by thread T3 here:
#0 0x7f9a1dd6f7cf in __interceptor_malloc
../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145
#1 0x5650d04cb17f in nsinfo__get util/namespaces.c:244
#2 0x5650d04ab7df in map__new util/map.c:150
#3 0x5650d04a11f6 in machine__process_mmap2_event util/machine.c:1798
#4 0x5650d04a24bf in machine__process_event util/machine.c:2019
#5 0x5650d03e78b3 in perf_event__process util/event.c:567
#6 0x5650d056e3bb in perf_tool__process_synth_event
util/synthetic-events.c:65
#7 0x5650d05711a6 in perf_event__synthesize_mmap_events
util/synthetic-events.c:501
#8 0x5650d0572fc0 in __event__synthesize_thread util/synthetic-events.c:792
#9 0x5650d05739fd in __perf_event__synthesize_threads
util/synthetic-events.c:929
#10 0x5650d0573cbd in synthesize_threads_worker util/synthetic-events.c:961
#11 0x7f9a1dc48d7f in start_thread nptl/pthread_create.c:481

Thread T6 created by T0 here:
#0 0x7f9a1dd17716 in __interceptor_pthread_create
../../../../src/libsanitizer/asan/asan_interceptors.cpp:216
#1 0x5650d05745eb in perf_event__synthesize_threads
util/synthetic-events.c:1039
#2 0x5650d05789fc in __machine__synthesize_threads
util/synthetic-events.c:1791
#3 0x5650d0578a81 in machine__synthesize_threads
util/synthetic-events.c:1802
#4 0x5650d024edd8 in __cmd_top
/usr/local/google/home/irogers/kernel-trees/kernel.org/tip/tools/perf/builtin-top.c:1273
#5 0x5650d025629b in cmd_top
/usr/local/google/home/irogers/kernel-trees/kernel.org/tip/tools/perf/builtin-top.c:1774
#6 0x5650d03b132b in run_builtin
/usr/local/google/home/irogers/kernel-trees/kernel.org/tip/tools/perf/perf.c:313
#7 0x5650d03b188d in handle_internal_command
/usr/local/google/home/irogers/kernel-trees/kernel.org/tip/tools/perf/perf.c:365
#8 0x5650d03b1c52 in run_argv
/usr/local/google/home/irogers/kernel-trees/kernel.org/tip/tools/perf/perf.c:409
#9 0x5650d03b246b in main
/usr/local/google/home/irogers/kernel-trees/kernel.org/tip/tools/perf/perf.c:539
#10 0x7f9a1cf077ec in __libc_start_main ../csu/libc-start.c:332

Thread T13 created by T0 here:
#0 0x7f9a1dd17716 in __interceptor_pthread_create
../../../../src/libsanitizer/asan/asan_interceptors.cpp:216
#1 0x5650d05745eb in perf_event__synthesize_threads
util/synthetic-events.c:1039
#2 0x5650d05789fc in __machine__synthesize_threads
util/synthetic-events.c:1791
```
That is thread 3 had created the wrapper object around the nsinfo,
thread 13 had put and freed it which cause a double free when thread 6
tried to do the same thing. How did thread 6 and 13 have the same
value for dso->nsinfo? In this patch we read then put the value, as
the put is slow another thread reads and puts the value too. We need
to atomically swap the value of dso->nsinfo with nsi and then do a put
on nsi which holds the old value of dso->nsinfo. The question is how
to do the swap?

C11 has atomic_exchange, but Makefile.config sets the std as gnu99.
C11 is used in some selftests. atomic_t and atomic_long_t aren't
guaranteed to be 64-bit, a long can be 32-bit with 64-bit pointers.
Using a non-atomic swap fixes the issue, memory leak, etc. but clearly
this needs to be atomic. My preference would be to bump to C11, but I
can do a linux atomic or poor man's swap if others prefer. Wdyt?

Thanks,
Ian

On Tue, Nov 30, 2021 at 9:20 AM Ian Rogers <irogers@google.com> wrote:
>
> On Tue, Nov 30, 2021 at 7:00 AM Arnaldo Carvalho de Melo
> <acme@kernel.org> wrote:
> >
> > Em Sun, Nov 28, 2021 at 04:40:26PM +0100, Jiri Olsa escreveu:
> > > On Thu, Nov 18, 2021 at 11:37:14AM -0800, Ian Rogers wrote:
> > > > This leak was happening reliably with test "Lookup mmap thread" with
> > > > stack traces like:
> > > >
> > > > Direct leak of 5504 byte(s) in 172 object(s) allocated from:
> > > > #0 0x7f4685e47987 in __interceptor_calloc
> > > > #1 0x56063b974c2a in nsinfo__new util/namespaces.c:142
> > > > #2 0x56063b9781ff in thread__new util/thread.c:70
> > > > #3 0x56063b944953 in ____machine__findnew_thread util/machine.c:543
> > > > #4 0x56063b944ac6 in __machine__findnew_thread util/machine.c:574
> > > > #5 0x56063b944b36 in machine__findnew_thread util/machine.c:584
> > > > #6 0x56063b94c892 in machine__process_fork_event util/machine.c:1954
> > > > #7 0x56063b94cc1f in machine__process_event util/machine.c:2019
> > > > #8 0x56063b894f18 in perf_event__process util/event.c:567
> > > > #9 0x56063ba17951 in perf_tool__process_synth_event util/synthetic-events.c:65
> > > > #10 0x56063ba19086 in perf_event__synthesize_fork util/synthetic-events.c:287
> > > > #11 0x56063ba1c39d in __event__synthesize_thread util/synthetic-events.c:775
> > > > #12 0x56063ba1cf6f in __perf_event__synthesize_threads util/synthetic-events.c:929
> > > > #13 0x56063ba1d4ab in perf_event__synthesize_threads util/synthetic-events.c:1000
> > > > #14 0x56063b821a3d in synth_all tests/mmap-thread-lookup.c:136
> > > > #15 0x56063b821c86 in mmap_events tests/mmap-thread-lookup.c:174
> > > > #16 0x56063b8221b7 in test__mmap_thread_lookup tests/mmap-thread-lookup.c:230
> > > >
> > > > The dso->nsinfo is overwritten, but without a nsinfo__put this can leak
> > > > the overwritten nsinfo.
> > > >
> > > > Signed-off-by: Ian Rogers <irogers@google.com>
> > >
> > > nice catch!
> > >
> > > Acked-by: Jiri Olsa <jolsa@redhat.com>
> >
> > This one is tricky, I have to retrieve the details from last time this
> > surfaced, but try:
> >
> > # perf top -F 10000
> >
> > leave it for a while and press 'q':
> >
> > perf: /home/acme/git/perf/tools/include/linux/refcount.h:131: refcount_sub_and_test: Assertion `!(new > val)' failed.
> > Aborted (core dumped)
> >
> > I reproduced the above assertion a few times, now I'm not being able,
> > probably some namespace related activity took place when it hit.
>
> I was able to reproduce in about 1 run in 3. With address sanitizer
> the core dump turns into a heap-use-after-free with a report of:
>
> ==235440==ERROR: AddressSanitizer: heap-use-after-free on address
> 0x6030000485c8 at pc 0x55d8b882bfb7 bp 0x7fffd3426e90 sp
> 0x7fffd3426e88
> READ of size 4 at 0x6030000485c8 thread T0
> #0 0x55d8b882bfb6 in __read_once_size ./tools/include/linux/compiler.h:132
> #1 0x55d8b882bfb6 in atomic_read
> ./tools/include/asm/../../arch/x86/include/asm/atomic.h:28
> #2 0x55d8b882c35c in refcount_sub_and_test
> ./tools/include/linux/refcount.h:123
> #3 0x55d8b882c45e in refcount_dec_and_test
> ./tools/include/linux/refcount.h:148
> #4 0x55d8b882d4af in nsinfo__put util/namespaces.c:204
> #5 0x55d8b87adecd in __nsinfo__zput util/namespaces.h:65
> #6 0x55d8b87b4bcc in dso__delete util/dso.c:1327
> #7 0x55d8b87b4c8d in dso__put util/dso.c:1342
> #8 0x55d8b87fb23b in dsos__purge util/machine.c:182
> #9 0x55d8b87fb2e3 in dsos__exit util/machine.c:190
> #10 0x55d8b87fb46e in machine__exit util/machine.c:222
> #11 0x55d8b87fb715 in machines__exit util/machine.c:262
> #12 0x55d8b88149d2 in perf_session__delete util/session.c:305
> #13 0x55d8b85c0924 in cmd_top ./tools/perf/builtin-top.c:1781
> #14 0x55d8b87176b7 in run_builtin ./tools/perf/perf.c:313
> #15 0x55d8b8717c10 in handle_internal_command ./tools/perf/perf.c:365
> #16 0x55d8b8717fcd in run_argv ./tools/perf/perf.c:409
> #17 0x55d8b87187bc in main ./tools/perf/perf.c:539
>
> 0x6030000485c8 is located 24 bytes inside of 32-byte region
> [0x6030000485b0,0x6030000485d0)
> freed by thread T0 here:
> #0 0x7fb6e7c454d7 in __interceptor_free
> ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:127
> #1 0x55d8b882d41a in nsinfo__delete util/namespaces.c:192
> #2 0x55d8b882d4bf in nsinfo__put util/namespaces.c:205
> #3 0x55d8b87adecd in __nsinfo__zput util/namespaces.h:65
> #4 0x55d8b87b4bcc in dso__delete util/dso.c:1327
> #5 0x55d8b87b4c8d in dso__put util/dso.c:1342
> #6 0x55d8b87fb23b in dsos__purge util/machine.c:182
> #7 0x55d8b87fb2e3 in dsos__exit util/machine.c:190
> #8 0x55d8b87fb46e in machine__exit util/machine.c:222
> #9 0x55d8b87fb715 in machines__exit util/machine.c:262
> #10 0x55d8b88149d2 in perf_session__delete util/session.c:305
> #11 0x55d8b85c0924 in cmd_top ./tools/perf/builtin-top.c:1781
> #12 0x55d8b87176b7 in run_builtin ./tools/perf/perf.c:313
> #13 0x55d8b8717c10 in handle_internal_command ./tools/perf/perf.c:365
> #14 0x55d8b8717fcd in run_argv ./tools/perf/perf.c:409
> #15 0x55d8b87187bc in main ./tools/perf/perf.c:539
>
> previously allocated by thread T11 here:
> #0 0x7fb6e7c45987 in __interceptor_calloc
> ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
> #1 0x55d8b882ceaa in nsinfo__new util/namespaces.c:142
> #2 0x55d8b883047f in thread__new util/thread.c:70
> #3 0x55d8b87fcb93 in ____machine__findnew_thread util/machine.c:543
> #4 0x55d8b87fcd06 in __machine__findnew_thread util/machine.c:574
> #5 0x55d8b87fcd76 in machine__findnew_thread util/machine.c:584
> #6 0x55d8b8804ad2 in machine__process_fork_event util/machine.c:1954
> #7 0x55d8b8804e5f in machine__process_event util/machine.c:2019
> #8 0x55d8b874cf18 in perf_event__process util/event.c:567
> #9 0x55d8b88cfbd1 in perf_tool__process_synth_event
> util/synthetic-events.c:65
> #10 0x55d8b88d1306 in perf_event__synthesize_fork
> util/synthetic-events.c:287
> #11 0x55d8b88d461d in __event__synthesize_thread util/synthetic-events.c:775
> #12 0x55d8b88d51ef in __perf_event__synthesize_threads
> util/synthetic-events.c:929
> #13 0x55d8b88d54af in synthesize_threads_worker util/synthetic-events.c:961
> #14 0x7fb6e7b1eead in start_thread nptl/pthread_create.c:463
>
> Thread T11 created by T0 here:
> #0 0x7fb6e7bed716 in __interceptor_pthread_create
> ../../../../src/libsanitizer/asan/asan_interceptors.cpp:216
> #1 0x55d8b88d5ddd in perf_event__synthesize_threads
> util/synthetic-events.c:1039
> #2 0x55d8b88da3b8 in __machine__synthesize_threads
> util/synthetic-events.c:1791
> #3 0x55d8b88da43d in machine__synthesize_threads
> util/synthetic-events.c:1802
> #4 0x55d8b85b9378 in __cmd_top ./tools/perf/builtin-top.c:1273
> #5 0x55d8b85c0811 in cmd_top ./tools/perf/builtin-top.c:1774
> #6 0x55d8b87176b7 in run_builtin ./tools/perf/perf.c:313
> #7 0x55d8b8717c10 in handle_internal_command ./tools/perf/perf.c:365
> #8 0x55d8b8717fcd in run_argv ./tools/perf/perf.c:409
> #9 0x55d8b87187bc in main ./tools/perf/perf.c:539
>
> SUMMARY: AddressSanitizer: heap-use-after-free
> ./tools/include/linux/compiler.h:132 in __read_once_size
> Shadow bytes around the buggy address:
> 0x0c0680001060: fa fa fa fa fa fa fa fa fd fd fd fd fa fa fa fa
> 0x0c0680001070: fa fa fa fa fa fa fa fa fa fa fd fd fd fd fa fa
> 0x0c0680001080: fa fa fa fa fa fa fa fa fa fa fa fa fd fd fd fd
> 0x0c0680001090: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> 0x0c06800010a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> =>0x0c06800010b0: fa fa fa fa fa fa fd fd fd[fd]fa fa fa fa fa fa
> 0x0c06800010c0: fa fa fa fa fa fa fa fa fd fd fd fa fa fa fd fd
> 0x0c06800010d0: fd fa fa fa fd fd fd fd fa fa fd fd fd fa fa fa
> 0x0c06800010e0: fd fd fd fd fa fa fd fd fd fd fa fa fd fd fd fa
> 0x0c06800010f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fd fd
> 0x0c0680001100: fd fd fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> Shadow byte legend (one shadow byte represents 8 application bytes):
> Addressable: 00
> Partially addressable: 01 02 03 04 05 06 07
> Heap left redzone: fa
> Freed heap region: fd
> Stack left redzone: f1
> Stack mid redzone: f2
> Stack right redzone: f3
> Stack after return: f5
> Stack use after scope: f8
> Global redzone: f9
> Global init order: f6
> Poisoned by user: f7
> Container overflow: fc
> Array cookie: ac
> Intra object redzone: bb
> ASan internal: fe
> Left alloca redzone: ca
> Right alloca redzone: cb
> Shadow gap: cc
> ==235440==ABORTING
>
> My hope was to land this so that 'perf test' wouldn't have new
> failures caused by leak sanitizer. So one option could be to guard the
> change with an address sanitizer #ifdef. The larger fix is to rework
> the reference counting logic, but I'd really hope we could switch that
> work to being in a language like Rust to get us out of the current
> memory leak vs crash wac-a-mole.
>
> +Riccardo as he did some great and related fixes over the summer.
>
> Thanks,
> Ian
>
>
>
> > - Arnaldo
> >
> > > thanks,
> > > jirka
> > >
> > > > ---
> > > > tools/perf/util/map.c | 1 +
> > > > 1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> > > > index 8af693d9678c..ceed8f407bc0 100644
> > > > --- a/tools/perf/util/map.c
> > > > +++ b/tools/perf/util/map.c
> > > > @@ -192,6 +192,7 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
> > > > if (!(prot & PROT_EXEC))
> > > > dso__set_loaded(dso);
> > > > }
> > > > + nsinfo__put(dso->nsinfo);
> > > > dso->nsinfo = nsi;
> > > >
> > > > if (build_id__is_defined(bid))
> > > > --
> > > > 2.34.0.rc2.393.gf8c9666880-goog
> > > >
> >
> > --
> >
> > - Arnaldo

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