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bh=HXp4xsK2COsg/sk8cOxH3Dv6mSNqqIz2BKhEw9890PI=; b=Gi/bmFbl/b1xBv7ycLuMLf0Ay1GkdC5BaE/AKxsvHDsG3ztr6Y2NBDwNRFBPyVgcg5xgfr qNS/amqvZqy4niL/VsPDVxLwy8ohfEXqSQV9xVsJgLCnnWhee9EUj5TPKIAXSMkAS1xwYv 84E1sNaay8YBlDgzU2UMLaQEPTRakLs= X-MC-Unique: 8lfCwswKPPOobjzalGIpCg-1 From: Kevin Wolf To: qemu-block@nongnu.org Subject: [PULL 20/20] docs/secure-coding-practices: Describe how to use 'null-co' block driver Date: Wed, 2 Jun 2021 15:45:29 +0200 Message-Id: <20210602134529.231756-21-kwolf@redhat.com> In-Reply-To: <20210602134529.231756-1-kwolf@redhat.com> References: <20210602134529.231756-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.371, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, peter.maydell@linaro.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) From: Philippe Mathieu-Daud=C3=A9 Document that security reports must use 'null-co,read-zeroes=3Don' because otherwise the memory is left uninitialized (which is an on-purpose performance feature). Reviewed-by: Vladimir Sementsov-Ogievskiy Signed-off-by: Philippe Mathieu-Daud=C3=A9 Message-Id: <20210601162548.2076631-1-philmd@redhat.com> Signed-off-by: Kevin Wolf --- docs/devel/secure-coding-practices.rst | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/docs/devel/secure-coding-practices.rst b/docs/devel/secure-cod= ing-practices.rst index cbfc8af67e..0454cc527e 100644 --- a/docs/devel/secure-coding-practices.rst +++ b/docs/devel/secure-coding-practices.rst @@ -104,3 +104,12 @@ structures and only process the local copy. This prev= ents time-of-check-to-time-of-use (TOCTOU) race conditions that could cause QEM= U to crash when a vCPU thread modifies guest RAM while device emulation is processing it. + +Use of null-co block drivers +---------------------------- + +The ``null-co`` block driver is designed for performance: its read accesse= s are +not initialized by default. In case this driver has to be used for security +research, it must be used with the ``read-zeroes=3Don`` option which fills= read +buffers with zeroes. Security issues reported with the default +(``read-zeroes=3Doff``) will be discarded. --=20 2.30.2