RE: [PATCH 0/9] tools subsystem refcounter conversions
From: Reshetova, Elena
Date: Thu Feb 23 2017 - 06:39:29 EST
> Em Wed, Feb 22, 2017 at 08:23:29PM -0300, Arnaldo Carvalho de Melo
> > Em Tue, Feb 21, 2017 at 12:39:35PM -0300, Arnaldo Carvalho de Melo
> > > 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:
And more specifically to this chunk:
@@ -937,7 +937,7 @@
map->base = NULL;
map->fd = -1;
- atomic_set(&map->refcnt, 0);
+ refcount_set(&map->refcnt, 0);
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."
> > 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.