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/+/58d561...
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);}
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.