linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: syzkaller <syzkaller@googlegroups.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Kostya Serebryany <kcc@google.com>,
	Alexander Potapenko <glider@google.com>,
	Eric Dumazet <edumazet@google.com>,
	Sasha Levin <sasha.levin@oracle.com>
Subject: Re: use-after-free in __perf_install_in_context
Date: Tue, 8 Dec 2015 10:05:30 -0800	[thread overview]
Message-ID: <20151208180528.GA77166@ast-mbp.thefacebook.com> (raw)
In-Reply-To: <CACT4Y+Y_w4oteNLKGE4gVqOpoyrmm+3VQDemGGScbepnXhL4VA@mail.gmail.com>

On Tue, Dec 08, 2015 at 06:56:23PM +0100, Dmitry Vyukov wrote:
> On Tue, Dec 8, 2015 at 6:54 PM, Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> > On Tue, Dec 08, 2015 at 05:12:04PM +0100, Dmitry Vyukov wrote:
> >> On Tue, Dec 8, 2015 at 4:24 AM, Alexei Starovoitov
> >> <alexei.starovoitov@gmail.com> wrote:
> >> > On Mon, Dec 07, 2015 at 05:09:21PM +0100, Dmitry Vyukov wrote:
> >> >> > So it would be _awesome_ if we could somehow extend this callchain to
> >> >> > include the site that calls call_rcu().
> >> >>
> >> >> We have a patch for KASAN in works that adds so-called stack depot
> >> >> which allows to map a stack trace onto uint32 id. Then we can plumb
> >> >
> >> > I was hacking something similar to categorize stack traces with u32 id.
> >> > How are you planning to limit the number of such stack traces ?
> >> > and what is the interface for user space to get stack trace from an id?
> >>
> >>
> >> We don't limit number of stack traces. Kernel does not seem to use
> >> data-driven recursion extensively, so there is limited number of
> >> stacks. Though, probably we will need to strip non-interrupt part for
> >> interrupt stacks, otherwise that can produce unbounded number of
> >> different stacks.
> >> There is no interface for user-space, it is used only inside of kernel
> >> to save stacks for memory blocks (rcu callbacks, thread pool items in
> >> the future).
> >> The design is based on what we successfully and extensively use in
> >> user-space sanitizers for years. Current code is here:
> >> https://github.com/ramosian-glider/kasan/commit/fb0eefd212366401ed5ad244233ef379a27bfb46
> >
> > why did you pick approach to never free accumulated stacks?
> > That limits usability a lot, since once kasan starts using it only
> > reboot will free the memory. ouch.
> > what worked for user space doesn't work for kernel.
> 
> 
> Freeing and reusing will slow down and complicate code significantly.
> And it is not yet proved to be necessary.

It's a joke, right? allocating kernel pages without ability to free?!


  reply	other threads:[~2015-12-08 18:05 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-04 20:04 use-after-free in __perf_install_in_context Dmitry Vyukov
2015-12-04 20:32 ` Alexei Starovoitov
2015-12-04 21:00   ` Dmitry Vyukov
2015-12-07 11:04     ` Dmitry Vyukov
2015-12-07 11:06       ` Dmitry Vyukov
2015-12-07 11:24         ` Dmitry Vyukov
2015-12-07 15:36 ` Peter Zijlstra
2015-12-07 16:09   ` Dmitry Vyukov
2015-12-08  3:24     ` Alexei Starovoitov
2015-12-08 16:12       ` Dmitry Vyukov
2015-12-08 17:54         ` Alexei Starovoitov
2015-12-08 17:56           ` Dmitry Vyukov
2015-12-08 18:05             ` Alexei Starovoitov [this message]
2015-12-08 18:35               ` Dmitry Vyukov
2015-12-08 19:56                 ` Alexei Starovoitov
2015-12-09  9:17                   ` Dmitry Vyukov
2015-12-10  3:54                     ` Alexei Starovoitov
2015-12-10  9:02                       ` Peter Zijlstra
2015-12-10 17:03                         ` Alexei Starovoitov
2015-12-11  8:14                           ` Ingo Molnar
2015-12-15 13:11                             ` Dmitry Vyukov
2015-12-08 16:44     ` Peter Zijlstra
2015-12-08 19:14       ` Dmitry Vyukov
2015-12-10 19:57         ` Peter Zijlstra
2015-12-15 13:09           ` Dmitry Vyukov
2015-12-17 14:06           ` Peter Zijlstra
2015-12-17 14:08             ` Dmitry Vyukov
2015-12-17 14:26               ` Peter Zijlstra
2015-12-17 14:28                 ` Peter Zijlstra
2015-12-17 14:35                   ` Dmitry Vyukov
2015-12-17 14:43                     ` Peter Zijlstra
2015-12-31 17:15                       ` Dmitry Vyukov
2016-01-05 12:17                         ` Peter Zijlstra
2016-01-08  8:40                           ` Dmitry Vyukov
2016-01-08 10:28                             ` Dmitry Vyukov
2016-01-06 18:46           ` [tip:perf/core] perf: Fix race in perf_event_exec() tip-bot for Peter Zijlstra
2016-01-06 18:56             ` Eric Dumazet
2016-01-07 13:40               ` Peter Zijlstra
2016-01-07 16:26                 ` Paul E. McKenney
2016-01-07 16:36                   ` Eric Dumazet
2016-01-07 16:46                     ` Paul E. McKenney
2015-12-08 16:22 ` use-after-free in __perf_install_in_context Peter Zijlstra
2015-12-08 18:57   ` Ingo Molnar
2015-12-09  9:05     ` Peter Zijlstra
2015-12-08 16:27 ` Peter Zijlstra
2015-12-08 16:50   ` Dmitry Vyukov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20151208180528.GA77166@ast-mbp.thefacebook.com \
    --to=alexei.starovoitov@gmail.com \
    --cc=acme@kernel.org \
    --cc=dvyukov@google.com \
    --cc=edumazet@google.com \
    --cc=glider@google.com \
    --cc=kcc@google.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=sasha.levin@oracle.com \
    --cc=syzkaller@googlegroups.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).