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Mon, 11 Jan 2021 09:09:24 -0800 (PST) MIME-Version: 1.0 References: <20210108205857.1471269-1-surenb@google.com> <875z43rd0u.fsf@oldenburg2.str.redhat.com> In-Reply-To: From: Suren Baghdasaryan Date: Mon, 11 Jan 2021 09:09:13 -0800 Message-ID: Subject: Re: [PATCH 1/1] mm/madvise: replace ptrace attach requirement for process_madvise To: Florian Weimer Cc: Andrew Morton , Jann Horn , Kees Cook , Jeffrey Vander Stoep , Minchan Kim , Michal Hocko , Shakeel Butt , David Rientjes , =?UTF-8?Q?Edgar_Arriaga_Garc=C3=ADa?= , Tim Murray , linux-mm , selinux@vger.kernel.org, Linux API , LKML , kernel-team Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jan 11, 2021 at 9:05 AM Suren Baghdasaryan wrote: > > On Mon, Jan 11, 2021 at 2:20 AM Florian Weimer 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. > V2 with Minchan's fix is posted at: https://lore.kernel.org/lkml/20210111170622.2613577-1-surenb@google.com/T/#u > > > > 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@android.com. > >