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Mon, 30 Oct 2023 15:12:12 -0700 (PDT) Date: Mon, 30 Oct 2023 15:12:10 -0700 In-Reply-To: Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-9-seanjc@google.com> <211d093f-4023-4a39-a23f-6d8543512675@redhat.com> Message-ID: Subject: Re: [PATCH v13 08/35] KVM: Introduce KVM_SET_USER_MEMORY_REGION2 From: Sean Christopherson To: Paolo Bonzini Cc: Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xiaoyao Li , Xu Yilun , Chao Peng , Fuad Tabba , Jarkko Sakkinen , Anish Moorthy , David Matlack , Yu Zhang , Isaku Yamahata , "=?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?=" , Vlastimil Babka , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A . Shutemov" Content-Type: text/plain; charset="us-ascii" X-Rspamd-Queue-Id: 5F87EC001E X-Rspam-User: X-Stat-Signature: o4qcx39snpab3hydj6j9s7xnq4r18j5p X-Rspamd-Server: rspam03 X-HE-Tag: 1698703933-515443 X-HE-Meta: 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 q7rvF7+v 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 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 Mon, Oct 30, 2023, Sean Christopherson wrote: > On Mon, Oct 30, 2023, Paolo Bonzini wrote: > > On 10/27/23 20:21, Sean Christopherson wrote: > > > > > > + if (ioctl == KVM_SET_USER_MEMORY_REGION) > > > + size = sizeof(struct kvm_userspace_memory_region); > > > > This also needs a memset(&mem, 0, sizeof(mem)), otherwise the out-of-bounds > > access of the commit message becomes a kernel stack read. > > Ouch. There's some irony. Might be worth doing memset(&mem, -1, sizeof(mem)) > though as '0' is a valid file descriptor and a valid file offset. > > > Probably worth adding a check on valid flags here. > > Definitely needed. There's a very real bug here. But rather than duplicate flags > checking or plumb @ioctl all the way to __kvm_set_memory_region(), now that we > have the fancy guard(mutex) and there are no internal calls to kvm_set_memory_region(), > what if we: > > 1. Acquire/release slots_lock in __kvm_set_memory_region() Gah, this won't work with x86's usage, which acquire slots_lock quite far away from __kvm_set_memory_region() in several places. The rest of the idea still works, kvm_vm_ioctl_set_memory_region() will just need to take slots_lock manually. > 2. Call kvm_set_memory_region() from x86 code for the internal memslots > 3. Disallow *any* flags for internal memslots > 4. Open code check_memory_region_flags in kvm_vm_ioctl_set_memory_region() > 5. Pass @ioctl to kvm_vm_ioctl_set_memory_region() and allow KVM_MEM_PRIVATE > only for KVM_SET_USER_MEMORY_REGION2