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[91.12.101.77]) by smtp.gmail.com with ESMTPSA id k26sm12161337wms.39.2021.09.27.02.29.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Sep 2021 02:29:59 -0700 (PDT) Subject: Re: [RFC PATCH] userfaultfd: support control over mm of remote PIDs To: Nadav Amit , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Nadav Amit , Andrea Arcangeli , Mike Rapoport , Peter Xu References: <20210926170637.245699-1-namit@vmware.com> From: David Hildenbrand Organization: Red Hat Message-ID: <83827672-0996-4c25-9991-697ad443b6b3@redhat.com> Date: Mon, 27 Sep 2021 11:29:59 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210926170637.245699-1-namit@vmware.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4174810328D0 X-Stat-Signature: 33h89zawar5mcsxt96t5xw8fdkwz1ate Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=gtJ8aPC0; spf=none (imf13.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam06 X-HE-Tag: 1632735004-209432 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 26.09.21 19:06, Nadav Amit wrote: > From: Nadav Amit > > Non-cooperative mode is useful but only for forked processes. > Userfaultfd can be useful to monitor, debug and manage memory of remote > processes. > > To support this mode, add a new flag, UFFD_REMOTE_PID, and an optional > second argument to the userfaultfd syscall. When the flag is set, the > second argument is assumed to be the PID of the process that is to be > monitored. Otherwise the flag is ignored. > > The syscall enforces that the caller has CAP_SYS_PTRACE to prevent > misuse of this feature. What supposed to happen if the target process intents to use uffd itself? -- Thanks, David / dhildenb