From: Suren Baghdasaryan <surenb@google.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Colin Cross <ccross@google.com>,
Sumit Semwal <sumit.semwal@linaro.org>,
Dave Hansen <dave.hansen@intel.com>,
Kees Cook <keescook@chromium.org>,
Matthew Wilcox <willy@infradead.org>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Vlastimil Babka <vbabka@suse.cz>,
Johannes Weiner <hannes@cmpxchg.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Christian Brauner <brauner@kernel.org>,
legion@kernel.org, ran.xiaokai@zte.com.cn, sashal@kernel.org,
Chris Hyser <chris.hyser@oracle.com>,
Davidlohr Bueso <dave@stgolabs.net>,
Peter Collingbourne <pcc@google.com>,
caoxiaofeng@yulong.com, David Hildenbrand <david@redhat.com>,
Cyrill Gorcunov <gorcunov@gmail.com>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-team <kernel-team@android.com>,
syzbot+aa7b3d4b35f9dc46a366@syzkaller.appspotmail.com
Subject: Re: [PATCH v3 1/1] mm: fix use-after-free when anon vma name is used after vma is freed
Date: Thu, 17 Feb 2022 11:54:00 -0800 [thread overview]
Message-ID: <CAJuCfpFOy_oRp=WWqtzE7bJR7p51FzzBPtbKhWeTGOKC-n41Cg@mail.gmail.com> (raw)
In-Reply-To: <YgywnF8l4Zu0aLtF@dhcp22.suse.cz>
On Wed, Feb 16, 2022 at 12:06 AM Michal Hocko <mhocko@suse.com> wrote:
>
> On Tue 15-02-22 15:02:54, Suren Baghdasaryan wrote:
> > On Tue, Feb 15, 2022 at 12:05 PM Michal Hocko <mhocko@suse.com> wrote:
> > >
> > > One thing I was considering is to check agains ref counte overflo (a
> > > deep process chain with many vmas could grow really high. ref_count
> > > interface doesn't provide any easy way to check for overflows as far as
> > > I could see from a quick glance so I gave up there but the logic would
> > > be really straightforward. We just create a new anon_vma_name with the same
> > > content and use it when duplicating if the usage grow really
> > > (arbitrarily) high.
> >
> > I went over proposed changes. I see a couple small required fixes
> > (resetting the name to NULL seems to be missing and I think
> > dup_vma_anon_name needs some tweaking) but overall quite
> > straight-forward.
>
> OK, great that this makes sense to you. As I've said I didn't really go
> into details, not even dared to boot that to test. So it will very
> likely need some more work but I do not expect this to grow much.
>
> > I'll post a separate patch to do this refactoring.
> > The original patch is fixing the UAF issue, so I don't want to mix it
> > with refactoring. Please let me know if you see an issue with
> > separating it that way.
>
> Well, I am not sure TBH. Look at diffstats. Your fix
> 2 files changed, 63 insertions(+), 17 deletions(-)
> the refactoring which should fix this and potentially others that might
> be still lurking there (because mixing shared pointers and their internal
> objects just begs for problems) is
> 7 files changed, 63 insertions(+), 86 deletions(-)
>
> more files touched for sure but the net result is much more clear and a
> much more code removed.
> The overflow logic would make it bigger but I guess the existing scheme
> needs it as well.
Ok, I'll see how to slice it after it's complete and tested.
Thanks for the input!
>
> I would also claim that both approaches are really painful to review
> because the existing model spreads into several areas and it is not
> really clear you caught them all just by staring into the diff so both
> will be rather painful to backport to older kernels. Fortunately this
> would be only 5.17.
> --
> Michal Hocko
> SUSE Labs
next prev parent reply other threads:[~2022-02-17 19:54 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-11 1:30 [PATCH v3 1/1] mm: fix use-after-free when anon vma name is used after vma is freed Suren Baghdasaryan
2022-02-15 16:00 ` Michal Hocko
2022-02-15 17:36 ` Suren Baghdasaryan
2022-02-15 19:47 ` Michal Hocko
2022-02-15 20:05 ` Michal Hocko
2022-02-15 23:02 ` Suren Baghdasaryan
2022-02-16 8:06 ` Michal Hocko
2022-02-17 19:54 ` Suren Baghdasaryan [this message]
2022-02-22 5:48 ` Suren Baghdasaryan
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='CAJuCfpFOy_oRp=WWqtzE7bJR7p51FzzBPtbKhWeTGOKC-n41Cg@mail.gmail.com' \
--to=surenb@google.com \
--cc=akpm@linux-foundation.org \
--cc=brauner@kernel.org \
--cc=caoxiaofeng@yulong.com \
--cc=ccross@google.com \
--cc=chris.hyser@oracle.com \
--cc=dave.hansen@intel.com \
--cc=dave@stgolabs.net \
--cc=david@redhat.com \
--cc=ebiederm@xmission.com \
--cc=gorcunov@gmail.com \
--cc=hannes@cmpxchg.org \
--cc=keescook@chromium.org \
--cc=kernel-team@android.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=legion@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=pcc@google.com \
--cc=ran.xiaokai@zte.com.cn \
--cc=sashal@kernel.org \
--cc=sumit.semwal@linaro.org \
--cc=syzbot+aa7b3d4b35f9dc46a366@syzkaller.appspotmail.com \
--cc=vbabka@suse.cz \
--cc=willy@infradead.org \
/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).