linux-kernel - Re: [PATCH 1/1] mm/madvise: replace ptrace attach requirement for process

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJuCfpGwer93uKRE3nqtmLwsUnK_Cn-Zz1bXuFGX94mmVxqQZg@mail.gmail.com>
Date:   Mon, 11 Jan 2021 09:05:37 -0800
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Florian Weimer <fweimer@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Jeffrey Vander Stoep <jeffv@...gle.com>,
        Minchan Kim <minchan@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Edgar Arriaga García <edgararriaga@...gle.com>,
        Tim Murray <timmurray@...gle.com>,
        linux-mm <linux-mm@...ck.org>, selinux@...r.kernel.org,
        Linux API <linux-api@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-team <kernel-team@...roid.com>
Subject: Re: [PATCH 1/1] mm/madvise: replace ptrace attach requirement for process_madvise

On Mon, Jan 11, 2021 at 2:20 AM Florian Weimer <fweimer@...hat.com> wrote:
>
> * Suren Baghdasaryan:
>
> > diff --git a/mm/madvise.c b/mm/madvise.c
> > index 6a660858784b..c2d600386902 100644
> > --- a/mm/madvise.c
> > +++ b/mm/madvise.c
> > @@ -1197,12 +1197,22 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
> >               goto release_task;
> >       }
> >
> > -     mm = mm_access(task, PTRACE_MODE_ATTACH_FSCREDS);
> > +     /* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */
> > +     mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
> >       if (IS_ERR_OR_NULL(mm)) {
> >               ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
> >               goto release_task;
> >       }
>
> Shouldn't this depend on the requested behavior?  Several operations
> directly result in observable changes, and go beyond performance tuning.

Thanks for the comment Florian.
process_madvise supports only MADV_COLD and MADV_PAGEOUT hints which
are both non-destructive (see process_madvise_behavior_valid()
function). Maybe you meant something else by "observable changes", if
so please clarify.
Thanks,
Suren.

>
> Thanks,
> Florian
> --
> Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn,
> Commercial register: Amtsgericht Muenchen, HRB 153243,
> Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill
>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@...roid.com.
>