user/sven/linux.git/include/linux/kvm_host.h, branch v4.4.295

kvm: fix previous commit for 32-bit builds

2021-06-16T09:34:53Z

commit 4422829e8053068e0225e4d0ef42dc41ea7c9ef5 upstream. array_index_nospec does not work for uint64_t on 32-bit builds. However, the size of a memory slot must be less than 20 bits wide on those system, since the memory slot must fit in the user address space. So just store it in an unsigned long. Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

kvm: avoid speculation-based attacks from out-of-range memslot accesses

2021-06-16T09:34:52Z

commit da27a83fd6cc7780fea190e1f5c19e87019da65c upstream. KVM's mechanism for accessing guest memory translates a guest physical address (gpa) to a host virtual address using the right-shifted gpa (also known as gfn) and a struct kvm_memory_slot. The translation is performed in __gfn_to_hva_memslot using the following formula: hva = slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZE It is expected that gfn falls within the boundaries of the guest's physical memory. However, a guest can access invalid physical addresses in such a way that the gfn is invalid. __gfn_to_hva_memslot is called from kvm_vcpu_gfn_to_hva_prot, which first retrieves a memslot through __gfn_to_memslot. While __gfn_to_memslot does check that the gfn falls within the boundaries of the guest's physical memory or not, a CPU can speculate the result of the check and continue execution speculatively using an illegal gfn. The speculation can result in calculating an out-of-bounds hva. If the resulting host virtual address is used to load another guest physical address, this is effectively a Spectre gadget consisting of two consecutive reads, the second of which is data dependent on the first. Right now it's not clear if there are any cases in which this is exploitable. One interesting case was reported by the original author of this patch, and involves visiting guest page tables on x86. Right now these are not vulnerable because the hva read goes through get_user(), which contains an LFENCE speculation barrier. However, there are patches in progress for x86 uaccess.h to mask kernel addresses instead of using LFENCE; once these land, a guest could use speculation to read from the VMM's ring 3 address space. Other architectures such as ARM already use the address masking method, and would be susceptible to this same kind of data-dependent access gadgets. Therefore, this patch proactively protects from these attacks by masking out-of-bounds gfns in __gfn_to_hva_memslot, which blocks speculation of invalid hvas. Sean Christopherson noted that this patch does not cover kvm_read_guest_offset_cached. This however is limited to a few bytes past the end of the cache, and therefore it is unlikely to be useful in the context of building a chain of data dependent accesses. Reported-by: Artemiy Margaritov Co-developed-by: Artemiy Margaritov Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

KVM: Check validity of resolved slot when searching memslots

2020-05-02T15:20:47Z

commit b6467ab142b708dd076f6186ca274f14af379c72 upstream. Check that the resolved slot (somewhat confusingly named 'start') is a valid/allocated slot before doing the final comparison to see if the specified gfn resides in the associated slot. The resolved slot can be invalid if the binary search loop terminated because the search index was incremented beyond the number of used slots. This bug has existed since the binary search algorithm was introduced, but went unnoticed because KVM statically allocated memory for the max number of slots, i.e. the access would only be truly out-of-bounds if all possible slots were allocated and the specified gfn was less than the base of the lowest memslot. Commit 36947254e5f98 ("KVM: Dynamically size memslot array based on number of used slots") eliminated the "all possible slots allocated" condition and made the bug embarrasingly easy to hit. Fixes: 9c1a5d38780e6 ("kvm: optimize GFN to memslot lookup with large slots amount") Reported-by: syzbot+d889b59b2bb87d4047a2@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-Id: <20200408064059.8957-2-sean.j.christopherson@intel.com> Reviewed-by: Cornelia Huck Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

KVM: kvm_io_bus_unregister_dev() should never fail

2017-04-08T07:53:32Z

commit 90db10434b163e46da413d34db8d0e77404cc645 upstream. No caller currently checks the return value of kvm_io_bus_unregister_dev(). This is evil, as all callers silently go on freeing their device. A stale reference will remain in the io_bus, getting at least used again, when the iobus gets teared down on kvm_destroy_vm() - leading to use after free errors. There is nothing the callers could do, except retrying over and over again. So let's simply remove the bus altogether, print an error and make sure no one can access this broken bus again (returning -ENOMEM on any attempt to access it). Fixes: e93f8a0f821e ("KVM: convert io_bus to SRCU") Reported-by: Dmitry Vyukov Reviewed-by: Cornelia Huck Signed-off-by: David Hildenbrand Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

KVM: Provide function for VCPU lookup by id

2015-11-19T13:25:32Z

Let's provide a function to lookup a VCPU by id. Reviewed-by: Christian Borntraeger Reviewed-by: Dominik Dingel Signed-off-by: David Hildenbrand Signed-off-by: Christian Borntraeger [split patch from refactoring patch]

KVM: x86: Add a common TSC scaling function

2015-11-10T11:06:15Z

VMX and SVM calculate the TSC scaling ratio in a similar logic, so this patch generalizes it to a common TSC scaling function. Signed-off-by: Haozhong Zhang [Inline the multiplication and shift steps into mul_u64_u64_shr. Remove BUG_ON. - Paolo] Signed-off-by: Paolo Bonzini

KVM: x86: move kvm_set_irq_inatomic to legacy device assignment

2015-11-04T15:24:36Z

The function is not used outside device assignment, and kvm_arch_set_irq_inatomic has a different prototype. Move it here and make it static to avoid confusion. Reviewed-by: Radim Krčmář Signed-off-by: Paolo Bonzini

KVM: x86: merge kvm_arch_set_irq with kvm_set_msi_inatomic

2015-11-04T15:24:35Z

We do not want to do too much work in atomic context, in particular not walking all the VCPUs of the virtual machine. So we want to distinguish the architecture-specific injection function for irqfd from kvm_set_msi. Since it's still empty, reuse the newly added kvm_arch_set_irq and rename it to kvm_arch_set_irq_inatomic. Reviewed-by: Radim Krčmář Signed-off-by: Paolo Bonzini

Merge tag 'kvm-arm-for-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD

2015-11-04T15:24:17Z

KVM/ARM Changes for v4.4-rc1 Includes a number of fixes for the arch-timer, introducing proper level-triggered semantics for the arch-timers, a series of patches to synchronously halt a guest (prerequisite for IRQ forwarding), some tracepoint improvements, a tweak for the EL2 panic handlers, some more VGIC cleanups getting rid of redundant state, and finally a stylistic change that gets rid of some ctags warnings. Conflicts: arch/x86/include/asm/kvm_host.h

KVM: Add kvm_arch_vcpu_{un}blocking callbacks

2015-10-22T21:01:41Z

Some times it is useful for architecture implementations of KVM to know when the VCPU thread is about to block or when it comes back from blocking (arm/arm64 needs to know this to properly implement timers, for example). Therefore provide a generic architecture callback function in line with what we do elsewhere for KVM generic-arch interactions. Reviewed-by: Marc Zyngier Signed-off-by: Christoffer Dall