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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250603-uffd-fixes-v1-1-9c638c73f047@columbia.edu> 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