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Donenfeld" , David Hildenbrand , Alexander Viro , Christian Brauner , Jan Kara , Pavel Emelyanov , Andrea Arcangeli , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 1/3] userfaultfd: correctly prevent registering VM_DROPPABLE regions Message-ID: References: <20250603-uffd-fixes-v1-0-9c638c73f047@columbia.edu> <20250603-uffd-fixes-v1-1-9c638c73f047@columbia.edu> MIME-Version: 1.0 In-Reply-To: <20250603-uffd-fixes-v1-1-9c638c73f047@columbia.edu> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xLimBN1IgsKsAFQdSjSM9apfR-UzAw4JCOuFBo9o82w_1749050230 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspam-User: X-Rspamd-Queue-Id: 3634B4000B X-Rspamd-Server: rspam09 X-Stat-Signature: kg8d1qbyygpu9q6c8nujf1jd854upk5b X-HE-Tag: 1749050232-621016 X-HE-Meta: U2FsdGVkX1/IhWwB4u/TY4Hd52SVTmENSQ4PtUASdEBlE/fQ7ziaIysDT75od0f0Zo9ggF1U4rj8FE7bzV2AqWxP0CgMced0jbkAp5NZ/p+c0CPNzry6jpbZ4k3iB7IuAbKPrjpzmB/Za99wVNaPwLVasD8PRZSy4WjdtVZCGDD7LzjXiHZqVyvVLbjmw84sP+XFRprNM/fJI4Omzn+aPVGhy0DGS0hgZDy+foOjL2Lnx/VYGA6R5tPeFxOZz4VtoXbScOyA9Xe/8Stkb0IlwZs4xXk9x4frUue577u0VIk+Dg3OElhxOgpDEzDBR6L/4Tcj16P4ivzt1GAXadAIuvbAKiYei/PYkp/Vj8jdpNGEvdGgCAfQ3aj0A10KulDs2eH/obV0hZnZit4JqmukwkcTo0X3NxfI2+GWG3U+/8nYgA+dxXCgVwKVcRepO2x7wXuM9GWu8leQGPmb4qZ+6nKmJ0g2Jn8BhYsprOiabzKzD5sXoFnVClLERD0sMa5oWXefi8J1+y7y1i1CrfCxWOA8ldQm9pGy2kBInyooaSRE5sB7ufCJ5FXL6jk+khYZvAqjZE+iKcdsYBP1s6GrWjCth3pfkeTjiUjb31vJ+I9TmqXLGat8XJqZHbLPl8LeFdoZHSjl5FjMFq82r9dO1YlVnYsTvA3txgulylxSxTIr8N98lz5HbOOa5qZHGE47UNmhBja5/xnJQu/+jIstQovfJF8/hnO6HFyVQWr0jhtyY6WPxxfrgu/KYUKknc2rU2hBLVaBY+JcpYVDSzjeOu+Xb0Mnj7GXVYW/dYycfyhUIFKWiQZB52eYLK+jKzgZrd/5gBOvbj/5OyyS5cl6lA4Xj+n7frSyM6KSl5VoaJRYunGcGcEheSj61jkCmNRZeQ6CneilG7JSBx+dAys5McK509BJRd64U8zO4Nv/p+Kvqk3ezSqdzS9ns+9wQ+H0lxVsOTgchRQYUhc13bl eAFCmmMz cPZ/DuOtQ7U+Yb50lWO8WsL/E+C5SRZ1PypZ48QL1Yu53FzAspvH9tR5CbrDRntOF9ASk5b+ZZ3sIwidKVScf7tfApSGNzlkvaHuhSf30cIPKeZmoQ4jIsZngHITPDB4EG0YZ8Ws2NuRMYOXa+vdcXTGkGNr7CrDoRNf8RQSjmxZGsDJGgc0aI1iZikOqycEF9vflXR5Gk1Vl1+QzS+1KtJ1CXZfMFv+ef1JUuxWld7vXiLY+OO9H8Y9vD7hjC6L7422/uOa9Xofioipt/Lw+QKdCYyH4ObWmOwXYBNbImZHsbGsLAZLIGS71Lui/KUFcjnGSNMreMVa/jSEbj9V1PqFLq4T4cVXhbnr4Aqie3IEzYaLnEgqwsBQRvYtfLNVzoXZkezzMgXbf8UsQZdXoZeTjcDFtvMAcENnv7L94Yc6ErzVmQtFE8klwGezVPlz3vVNPG5ycDBJY6jE= 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: List-Subscribe: List-Unsubscribe: On Tue, Jun 03, 2025 at 06:14:20PM -0400, Tal Zussman wrote: > vma_can_userfault() masks off non-userfaultfd VM flags from vm_flags. > The vm_flags & VM_DROPPABLE test will then always be false, incorrectly > allowing VM_DROPPABLE regions to be registered with userfaultfd. > > Additionally, vm_flags is not guaranteed to correspond to the actual > VMA's flags. Fix this test by checking the VMA's flags directly. > > Link: https://lore.kernel.org/linux-mm/5a875a3a-2243-4eab-856f-bc53ccfec3ea@redhat.com/ > Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings") > Signed-off-by: Tal Zussman Acked-by: Peter Xu -- Peter Xu