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Re: [PATCH 0/9] tools subsystem refcounter conversions

From Arnaldo Carvalho de Melo <acme@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH 0/9] tools subsystem refcounter conversions
Date 2017-02-23 14:00 +0100
Message-ID <te1a1-1n9-9@gated-at.bofh.it> (permalink)
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Em Thu, Feb 23, 2017 at 11:39:10AM +0000, Reshetova, Elena escreveu:
> > Em Wed, Feb 22, 2017 at 08:23:29PM -0300, Arnaldo Carvalho de Melo
> > escreveu:
> > > Em Tue, Feb 21, 2017 at 12:39:35PM -0300, Arnaldo Carvalho de Melo
> > escreveu:
> > > > Em Tue, Feb 21, 2017 at 05:34:54PM +0200, Elena Reshetova escreveu:
> > > > > Now when new refcount_t type and API are finally merged
> > > > > (see include/linux/refcount.h), the following
> > > > > patches convert various refcounters in the tools susystem from atomic_t
> > > > > to refcount_t. By doing this we prevent intentional or accidental
> > > > > underflows or overflows that can led to use-after-free vulnerabilities.
> > > >
> > > > Thanks for working on this! I was almost going to jump on doing this
> > > > myself!
> > > >
> > > > I'll try and get this merged ASAP.
> > >
> > > So, please take a look at my tmp.perf/refcount branch at:
> > >
> > > git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git
> 
> I took a look on it and it looks good. Just one thing I want to double check with regards to this commit:
> https://kernel.googlesource.com/pub/scm/linux/kernel/git/acme/linux/+/58d561002587bf2572f9e6f4d222659e4068fadf%5E%21/#F0
> 
> And more specifically to this chunk:
> 
> @@ -937,7 +937,7 @@
>  		munmap(map->base, perf_mmap__mmap_len(map));
>  		map->base = NULL;
>  		map->fd = -1;
> -		atomic_set(&map->refcnt, 0);
> +		refcount_set(&map->refcnt, 0);
>  	}
>  	auxtrace_mmap__munmap(&map->auxtrace_mmap);
>  }
 
> So, when the refcount set to zero in this place, what exactly happens
> to the perf_map object after?  I just want to double check that we
> don't have  another hiding reusage case here when refcounter later on
> is simply incremented vs. set to "2." 

So, this looks fishy and I don't recall why that was done that way, this
conversion to refcnt_t and the debug associated with it provides a good
opportunity for us to try to get that to a more familiar reference
counting workflow, I'll take a look at it.

- Arnaldo
 
> > > There are multiple fixes in it to get it to build and test it, so far,
> > > with:
> > >
> > >   perf top -F 15000 -d 0
> > >
> > > while doing kernel builds and tight usleep 1 loops to create lots of
> > > short lived threads with its map_groups, maps, dsos, etc.
> > >
> > > Now running some build tests in some 36 containers with assorted distros
> > > and cross compilers.
> > 
> > Tomorrow I'll inject some refcount errors to test this all.
> 
> 
> Thank you!
> 
> Best Regards,
> Elena.

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Thread

[PATCH 0/9] tools subsystem refcounter conversions Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 16:40 +0100
  [PATCH 9/9] tools: convert thread_map.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 16:40 +0100
  [PATCH 2/9] tools: convert cpu_map.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 16:40 +0100
    Re: [PATCH 2/9] tools: convert cpu_map.refcnt from atomic_t to  refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-22 21:40 +0100
  [PATCH 1/9] tools: convert cgroup_sel.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 16:40 +0100
    Re: [PATCH 1/9] tools: convert cgroup_sel.refcnt from atomic_t to  refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-21 16:50 +0100
      RE: [PATCH 1/9] tools: convert cgroup_sel.refcnt from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-22 15:30 +0100
        Re: [PATCH 1/9] tools: convert cgroup_sel.refcnt from atomic_t to  refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-22 16:50 +0100
          RE: [PATCH 1/9] tools: convert cgroup_sel.refcnt from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-22 17:20 +0100
            Re: [PATCH 1/9] tools: convert cgroup_sel.refcnt from atomic_t to  refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-22 21:40 +0100
              RE: [PATCH 1/9] tools: convert cgroup_sel.refcnt from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-23 14:20 +0100
  [PATCH 3/9] tools: convert comm_str.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 16:40 +0100
    Re: [PATCH 3/9] tools: convert comm_str.refcnt from atomic_t to  refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-22 21:40 +0100
      Re: [PATCH 3/9] tools: convert comm_str.refcnt from atomic_t to  refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-22 23:30 +0100
        Re: [PATCH 3/9] tools: convert comm_str.refcnt from atomic_t to  refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-22 23:40 +0100
          RE: [PATCH 3/9] tools: convert comm_str.refcnt from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-23 10:20 +0100
            Re: [PATCH 3/9] tools: convert comm_str.refcnt from atomic_t to  refcount_t Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-23 14:20 +0100
  Re: [PATCH 0/9] tools subsystem refcounter conversions Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-21 16:50 +0100
    Re: [PATCH 0/9] tools subsystem refcounter conversions Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-23 00:30 +0100
      Re: [PATCH 0/9] tools subsystem refcounter conversions Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-23 00:30 +0100
        RE: [PATCH 0/9] tools subsystem refcounter conversions "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-23 12:40 +0100
          Re: [PATCH 0/9] tools subsystem refcounter conversions Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-23 14:00 +0100
          Re: [PATCH 0/9] tools subsystem refcounter conversions Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-23 17:30 +0100
            RE: [PATCH 0/9] tools subsystem refcounter conversions "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-24 08:40 +0100
              Re: [PATCH 0/9] tools subsystem refcounter conversions Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-02-24 14:40 +0100
  Re: [PATCH 0/9] tools subsystem refcounter conversions Peter Zijlstra <peterz@infradead.org> - 2017-02-21 16:50 +0100
    RE: [PATCH 0/9] tools subsystem refcounter conversions "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-21 17:10 +0100

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