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Mon, 11 Jan 2021 10:20:06 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-113-100.ams2.redhat.com [10.36.113.100]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8048974449; Mon, 11 Jan 2021 10:20:03 +0000 (UTC) From: Florian Weimer To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, jannh@google.com, keescook@chromium.org, jeffv@google.com, minchan@kernel.org, mhocko@suse.com, shakeelb@google.com, rientjes@google.com, edgararriaga@google.com, timmurray@google.com, linux-mm@kvack.org, selinux@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 1/1] mm/madvise: replace ptrace attach requirement for process_madvise References: <20210108205857.1471269-1-surenb@google.com> Date: Mon, 11 Jan 2021 11:20:01 +0100 In-Reply-To: <20210108205857.1471269-1-surenb@google.com> (Suren Baghdasaryan's message of "Fri, 8 Jan 2021 12:58:57 -0800") Message-ID: <875z43rd0u.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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: * 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, 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