From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751282AbdBXHas convert rfc822-to-8bit (ORCPT ); Fri, 24 Feb 2017 02:30:48 -0500 Received: from mga04.intel.com ([192.55.52.120]:27755 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750924AbdBXHaj (ORCPT ); Fri, 24 Feb 2017 02:30:39 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.35,200,1484035200"; d="scan'208";a="1115013087" From: "Reshetova, Elena" To: Arnaldo Carvalho de Melo CC: "linux-kernel@vger.kernel.org" , "alsa-devel@alsa-project.org" , "peterz@infradead.org" , "gregkh@linuxfoundation.org" , "mingo@redhat.com" , "alexander.shishkin@linux.intel.com" , "jolsa@kernel.org" , "mark.rutland@arm.com" , "akpm@linux-foundation.org" , "matija.glavinic-pecotic.ext@nokia.com" Subject: RE: [PATCH 0/9] tools subsystem refcounter conversions Thread-Topic: [PATCH 0/9] tools subsystem refcounter conversions Thread-Index: AQHSjFgboS1/QuSgJEOtrvW1clfnTKFzmLeAgAIT8oCAAAGegIAAyk0QgABRIwCAAPrzEA== Date: Fri, 24 Feb 2017 07:27:32 +0000 Message-ID: <2236FBA76BA1254E88B949DDB74E612B41C4F9DA@IRSMSX102.ger.corp.intel.com> References: <1487691303-31858-1-git-send-email-elena.reshetova@intel.com> <20170221153935.GE5052@kernel.org> <20170222232329.GN20447@kernel.org> <20170222232917.GO20447@kernel.org> <2236FBA76BA1254E88B949DDB74E612B41C4F449@IRSMSX102.ger.corp.intel.com> <20170223162344.GD3595@kernel.org> In-Reply-To: <20170223162344.GD3595@kernel.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [163.33.239.180] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > 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/+/58d > 561002587bf2572f9e6f4d222659e4068fadf%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 is an odd use of a reference count, the patch below should help > understand it? Yes, it helps, indeed, but I think we have an issue here. See below inline in patch. > > Those perf_mmap objects are created in a batch fashion, it being zero > just means it isn't yet mmaped at all, and we check for that before > using it. > > So, it remains a bug to do a dec for a zeroed refcount, and the > refcount_t infrastructure will catch it, which helps tools/. > > - Arnaldo > > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c > index 564b924fb48a..5a70f08d2518 100644 > --- a/tools/perf/util/evlist.c > +++ b/tools/perf/util/evlist.c > @@ -974,8 +974,19 @@ static struct perf_mmap > *perf_evlist__alloc_mmap(struct perf_evlist *evlist) > if (!map) > return NULL; > > - for (i = 0; i < evlist->nr_mmaps; i++) > + for (i = 0; i < evlist->nr_mmaps; i++) { > map[i].fd = -1; > + /* > + * When the perf_mmap() call is made we grab > one refcount, plus > + * one extra to let perf_evlist__mmap_consume() > get the last > + * events after all real references > (perf_mmap__get()) are > + * dropped. > + * > + * Each PERF_EVENT_IOC_SET_OUTPUT points to > this mmap and > + * thus does perf_mmap__get() on it. > + */ > + refcount_set(&map[i].refcnt, 0); > + } > return map; > } > > @@ -988,6 +999,7 @@ struct mmap_params { > static int perf_mmap__mmap(struct perf_mmap *map, > struct mmap_params *mp, int fd) > { > + perf_mmap__get(map); > /* > * The last one will be done at perf_evlist__mmap_consume(), > so that we > * make sure we don't prevent tools from consuming every last > event in > @@ -1001,7 +1013,7 @@ static int perf_mmap__mmap(struct perf_mmap > *map, > * evlist layer can't just drop it when filtering events in > * perf_evlist__filter_pollfd(). > */ > - refcount_set(&map->refcnt, 2); > + perf_mmap__get(map); /* This is not a dup, see the comment > above! */ This change now means that instead of doing refcount_set to 2 when refcount value is "0", you are doing two refcount_inc() via perf_mmap__get(), which is not going to do any increments when refcount value is zero. So, in that sense having just one refcount_set to 2 with a good explanation why it is needed is better :) When I asked about it initially, I just wanted to make sure there are no other refcount_inc()s happening on the object when its refcount value is zero. Which looks to be the case apart from the one above. Best Regards, Elena. > map->prev = 0; > map->mask = mp->mask; > map->base = mmap(NULL, perf_mmap__mmap_len(map), mp- > >prot, > > > > > 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. From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Reshetova, Elena" Subject: Re: [PATCH 0/9] tools subsystem refcounter conversions Date: Fri, 24 Feb 2017 07:27:32 +0000 Message-ID: <2236FBA76BA1254E88B949DDB74E612B41C4F9DA@IRSMSX102.ger.corp.intel.com> References: <1487691303-31858-1-git-send-email-elena.reshetova@intel.com> <20170221153935.GE5052@kernel.org> <20170222232329.GN20447@kernel.org> <20170222232917.GO20447@kernel.org> <2236FBA76BA1254E88B949DDB74E612B41C4F449@IRSMSX102.ger.corp.intel.com> <20170223162344.GD3595@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by alsa0.perex.cz (Postfix) with ESMTP id 38AD2266FFF for ; Fri, 24 Feb 2017 08:27:39 +0100 (CET) In-Reply-To: <20170223162344.GD3595@kernel.org> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Arnaldo Carvalho de Melo Cc: "mark.rutland@arm.com" , "alsa-devel@alsa-project.org" , "peterz@infradead.org" , "gregkh@linuxfoundation.org" , "linux-kernel@vger.kernel.org" , "alexander.shishkin@linux.intel.com" , "mingo@redhat.com" , "matija.glavinic-pecotic.ext@nokia.com" , "jolsa@kernel.org" , "akpm@linux-foundation.org" List-Id: alsa-devel@alsa-project.org > 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/+/58d > 561002587bf2572f9e6f4d222659e4068fadf%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 is an odd use of a reference count, the patch below should help > understand it? Yes, it helps, indeed, but I think we have an issue here. See below inline in patch. > > Those perf_mmap objects are created in a batch fashion, it being zero > just means it isn't yet mmaped at all, and we check for that before > using it. > > So, it remains a bug to do a dec for a zeroed refcount, and the > refcount_t infrastructure will catch it, which helps tools/. > > - Arnaldo > > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c > index 564b924fb48a..5a70f08d2518 100644 > --- a/tools/perf/util/evlist.c > +++ b/tools/perf/util/evlist.c > @@ -974,8 +974,19 @@ static struct perf_mmap > *perf_evlist__alloc_mmap(struct perf_evlist *evlist) > if (!map) > return NULL; > > - for (i = 0; i < evlist->nr_mmaps; i++) > + for (i = 0; i < evlist->nr_mmaps; i++) { > map[i].fd = -1; > + /* > + * When the perf_mmap() call is made we grab > one refcount, plus > + * one extra to let perf_evlist__mmap_consume() > get the last > + * events after all real references > (perf_mmap__get()) are > + * dropped. > + * > + * Each PERF_EVENT_IOC_SET_OUTPUT points to > this mmap and > + * thus does perf_mmap__get() on it. > + */ > + refcount_set(&map[i].refcnt, 0); > + } > return map; > } > > @@ -988,6 +999,7 @@ struct mmap_params { > static int perf_mmap__mmap(struct perf_mmap *map, > struct mmap_params *mp, int fd) > { > + perf_mmap__get(map); > /* > * The last one will be done at perf_evlist__mmap_consume(), > so that we > * make sure we don't prevent tools from consuming every last > event in > @@ -1001,7 +1013,7 @@ static int perf_mmap__mmap(struct perf_mmap > *map, > * evlist layer can't just drop it when filtering events in > * perf_evlist__filter_pollfd(). > */ > - refcount_set(&map->refcnt, 2); > + perf_mmap__get(map); /* This is not a dup, see the comment > above! */ This change now means that instead of doing refcount_set to 2 when refcount value is "0", you are doing two refcount_inc() via perf_mmap__get(), which is not going to do any increments when refcount value is zero. So, in that sense having just one refcount_set to 2 with a good explanation why it is needed is better :) When I asked about it initially, I just wanted to make sure there are no other refcount_inc()s happening on the object when its refcount value is zero. Which looks to be the case apart from the one above. Best Regards, Elena. > map->prev = 0; > map->mask = mp->mask; > map->base = mmap(NULL, perf_mmap__mmap_len(map), mp- > >prot, > > > > > 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.