From: Suren Baghdasaryan <surenb@google.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Yang Shi <shy828301@gmail.com>,
syzbot <syzbot+2ccf63a4bd07cf39cab0@syzkaller.appspotmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Christian Brauner <brauner@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: [syzbot] KASAN: use-after-free Read in __oom_reap_task_mm
Date: Tue, 15 Feb 2022 12:30:12 -0800 [thread overview]
Message-ID: <CAJuCfpF0-xm-RzUmaA6uHQ974tGtg4F8jzTTOFbBLM8iUy4nFA@mail.gmail.com> (raw)
In-Reply-To: <CAJuCfpGixCqZDAqokxCrQ1YjMb+32Y77U5jHkULKM0htnR19MQ@mail.gmail.com>
On Tue, Feb 15, 2022 at 11:43 AM Suren Baghdasaryan <surenb@google.com> wrote:
>
> On Tue, Feb 15, 2022 at 11:36 AM Michal Hocko <mhocko@suse.com> wrote:
> >
> > On Tue 15-02-22 10:10:53, Suren Baghdasaryan wrote:
> > > On Tue, Feb 15, 2022 at 9:53 AM Yang Shi <shy828301@gmail.com> wrote:
> > [...]
> > > > Isn't the below race possible?
> > > >
> > > > CPU A CPU B
> > > > exiting:
> > > > mmap_write_lock
> > > > remove_vma()
> > > > mmap_write_unlock
> > > > process_mrelease:
> > > > mmap_read_lock
> > > > __oom_reap_task_mm
> > > > mmap_read_unlock
> > > >
> > >
> > > Sure, that sequence (would not call it a race) is possible but in this
> > > case __oom_reap_task_mm will find no vmas in the mm because exit_mmap
> > > freed and removed all of them.
> >
> > I didn't really have chance to have a closer look but I do not see
> > exit_mmap doing mm->mmap = NULL so the pointer can be a freed vma unless
> > I am missing something. I thought we've had it in your patches? Has this
> > got lost somewhere in the process?
>
> Doh! Yes, it looks like I completely missed the actual pointer. That
> must be it since I don't see any other possibility. Will post a patch
> shortly.
Fix posted at https://lore.kernel.org/all/20220215201922.1908156-1-surenb@google.com/
> Thanks!
>
> > --
> > Michal Hocko
> > SUSE Labs
prev parent reply other threads:[~2022-02-15 20:30 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-14 10:44 [syzbot] KASAN: use-after-free Read in __oom_reap_task_mm syzbot
2022-02-14 19:07 ` Yang Shi
2022-02-15 9:59 ` Michal Hocko
2022-02-15 17:34 ` Suren Baghdasaryan
2022-02-15 17:53 ` Yang Shi
2022-02-15 18:10 ` Suren Baghdasaryan
2022-02-15 19:36 ` Michal Hocko
2022-02-15 19:43 ` Suren Baghdasaryan
2022-02-15 20:30 ` Suren Baghdasaryan [this message]
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