linux-stable.git/virt, branch v4.19.37

KVM: Reject device ioctls from processes other than the VM's creator

2019-04-03T04:26:29+00:00

commit ddba91801aeb5c160b660caed1800eb3aef403f8 upstream.

KVM's API requires thats ioctls must be issued from the same process
that created the VM.  In other words, userspace can play games with a
VM's file descriptors, e.g. fork(), SCM_RIGHTS, etc..., but only the
creator can do anything useful.  Explicitly reject device ioctls that
are issued by a process other than the VM's creator, and update KVM's
API documentation to extend its requirements to device ioctls.

Fixes: 852b6d57dc7f ("kvm: add device control API")
Cc: 
Signed-off-by: Sean Christopherson 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman

KVM: Call kvm_arch_memslots_updated() before updating memslots

2019-03-23T19:10:13+00:00

commit 152482580a1b0accb60676063a1ac57b2d12daf6 upstream.

kvm_arch_memslots_updated() is at this point in time an x86-specific
hook for handling MMIO generation wraparound.  x86 stashes 19 bits of
the memslots generation number in its MMIO sptes in order to avoid
full page fault walks for repeat faults on emulated MMIO addresses.
Because only 19 bits are used, wrapping the MMIO generation number is
possible, if unlikely.  kvm_arch_memslots_updated() alerts x86 that
the generation has changed so that it can invalidate all MMIO sptes in
case the effective MMIO generation has wrapped so as to avoid using a
stale spte, e.g. a (very) old spte that was created with generation==0.

Given that the purpose of kvm_arch_memslots_updated() is to prevent
consuming stale entries, it needs to be called before the new generation
is propagated to memslots.  Invalidating the MMIO sptes after updating
memslots means that there is a window where a vCPU could dereference
the new memslots generation, e.g. 0, and incorrectly reuse an old MMIO
spte that was created with (pre-wrap) generation==0.

Fixes: e59dbe09f8e6 ("KVM: Introduce kvm_arch_memslots_updated()")
Cc: 
Signed-off-by: Sean Christopherson 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman

KVM: arm/arm64: vgic: Always initialize the group of private IRQs

2019-03-23T19:09:43+00:00

[ Upstream commit ab2d5eb03dbb7b37a1c6356686fb48626ab0c93e ]

We currently initialize the group of private IRQs during
kvm_vgic_vcpu_init, and the value of the group depends on the GIC model
we are emulating.  However, CPUs created before creating (and
initializing) the VGIC might end up with the wrong group if the VGIC
is created as GICv3 later.

Since we have no enforced ordering of creating the VGIC and creating
VCPUs, we can end up with part the VCPUs being properly intialized and
the remaining incorrectly initialized.  That also means that we have no
single place to do the per-cpu data structure initialization which
depends on knowing the emulated GIC model (which is only the group
field).

This patch removes the incorrect comment from kvm_vgic_vcpu_init and
initializes the group of all previously created VCPUs's private
interrupts in vgic_init in addition to the existing initialization in
kvm_vgic_vcpu_init.

Signed-off-by: Christoffer Dall 
Signed-off-by: Marc Zyngier 
Signed-off-by: Sasha Levin

arm/arm64: KVM: Allow a VCPU to fully reset itself

2019-03-23T19:09:43+00:00

[ Upstream commit 358b28f09f0ab074d781df72b8a671edb1547789 ]

The current kvm_psci_vcpu_on implementation will directly try to
manipulate the state of the VCPU to reset it.  However, since this is
not done on the thread that runs the VCPU, we can end up in a strangely
corrupted state when the source and target VCPUs are running at the same
time.

Fix this by factoring out all reset logic from the PSCI implementation
and forwarding the required information along with a request to the
target VCPU.

Reviewed-by: Andrew Jones 
Signed-off-by: Marc Zyngier 
Signed-off-by: Christoffer Dall 
Signed-off-by: Sasha Levin

KVM: arm/arm64: vgic: Make vgic_dist->lpi_list_lock a raw_spinlock

2019-03-23T19:09:42+00:00

[ Upstream commit fc3bc475231e12e9c0142f60100cf84d077c79e1 ]

vgic_dist->lpi_list_lock must always be taken with interrupts disabled as
it is used in interrupt context.

For configurations such as PREEMPT_RT_FULL, this means that it should
be a raw_spinlock since RT spinlocks are interruptible.

Signed-off-by: Julien Thierry 
Acked-by: Christoffer Dall 
Acked-by: Marc Zyngier 
Signed-off-by: Christoffer Dall 
Signed-off-by: Sasha Levin

kvm: fix kvm_ioctl_create_device() reference counting (CVE-2019-6974)

2019-02-12T18:47:25+00:00

commit cfa39381173d5f969daf43582c95ad679189cbc9 upstream.

kvm_ioctl_create_device() does the following:

1. creates a device that holds a reference to the VM object (with a borrowed
   reference, the VM's refcount has not been bumped yet)
2. initializes the device
3. transfers the reference to the device to the caller's file descriptor table
4. calls kvm_get_kvm() to turn the borrowed reference to the VM into a real
   reference

The ownership transfer in step 3 must not happen before the reference to the VM
becomes a proper, non-borrowed reference, which only happens in step 4.
After step 3, an attacker can close the file descriptor and drop the borrowed
reference, which can cause the refcount of the kvm object to drop to zero.

This means that we need to grab a reference for the device before
anon_inode_getfd(), otherwise the VM can disappear from under us.

Fixes: 852b6d57dc7f ("kvm: add device control API")
Cc: stable@kernel.org
Signed-off-by: Jann Horn 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman

kvm: Change offset in kvm_write_guest_offset_cached to unsigned

2019-02-12T18:47:16+00:00

[ Upstream commit 7a86dab8cf2f0fdf508f3555dddfc236623bff60 ]

Since the offset is added directly to the hva from the
gfn_to_hva_cache, a negative offset could result in an out of bounds
write. The existing BUG_ON only checks for addresses beyond the end of
the gfn_to_hva_cache, not for addresses before the start of the
gfn_to_hva_cache.

Note that all current call sites have non-negative offsets.

Fixes: 4ec6e8636256 ("kvm: Introduce kvm_write_guest_offset_cached()")
Reported-by: Cfir Cohen 
Signed-off-by: Jim Mattson 
Reviewed-by: Cfir Cohen 
Reviewed-by: Peter Shier 
Reviewed-by: Krish Sadhukhan 
Reviewed-by: Sean Christopherson 
Signed-off-by: Radim Krčmář 
Signed-off-by: Sasha Levin

arm64: KVM: Skip MMIO insn after emulation

2019-02-12T18:47:12+00:00

[ Upstream commit 0d640732dbebed0f10f18526de21652931f0b2f2 ]

When we emulate an MMIO instruction, we advance the CPU state within
decode_hsr(), before emulating the instruction effects.

Having this logic in decode_hsr() is opaque, and advancing the state
before emulation is problematic. It gets in the way of applying
consistent single-step logic, and it prevents us from being able to fail
an MMIO instruction with a synchronous exception.

Clean this up by only advancing the CPU state *after* the effects of the
instruction are emulated.

Cc: Peter Maydell 
Reviewed-by: Alex Bennée 
Reviewed-by: Christoffer Dall 
Signed-off-by: Mark Rutland 
Signed-off-by: Marc Zyngier 
Signed-off-by: Sasha Levin

KVM: arm/arm64: Fix VMID alloc race by reverting to lock-less

2019-01-16T21:04:37+00:00

commit fb544d1ca65a89f7a3895f7531221ceeed74ada7 upstream.

We recently addressed a VMID generation race by introducing a read/write
lock around accesses and updates to the vmid generation values.

However, kvm_arch_vcpu_ioctl_run() also calls need_new_vmid_gen() but
does so without taking the read lock.

As far as I can tell, this can lead to the same kind of race:

  VM 0, VCPU 0			VM 0, VCPU 1
  ------------			------------
  update_vttbr (vmid 254)
  				update_vttbr (vmid 1) // roll over
				read_lock(kvm_vmid_lock);
				force_vm_exit()
  local_irq_disable
  need_new_vmid_gen == false //because vmid gen matches

  enter_guest (vmid 254)
  				kvm_arch.vttbr = :
				read_unlock(kvm_vmid_lock);

  				enter_guest (vmid 1)

Which results in running two VCPUs in the same VM with different VMIDs
and (even worse) other VCPUs from other VMs could now allocate clashing
VMID 254 from the new generation as long as VCPU 0 is not exiting.

Attempt to solve this by making sure vttbr is updated before another CPU
can observe the updated VMID generation.

Cc: stable@vger.kernel.org
Fixes: f0cf47d939d0 "KVM: arm/arm64: Close VMID generation race"
Reviewed-by: Julien Thierry 
Signed-off-by: Christoffer Dall 
Signed-off-by: Marc Zyngier 
Signed-off-by: Greg Kroah-Hartman

KVM: arm/arm64: vgic: Fix off-by-one bug in vgic_get_irq()

2019-01-09T16:38:49+00:00

commit c23b2e6fc4ca346018618266bcabd335c0a8a49e upstream.

When using the nospec API, it should be taken into account that:

"...if the CPU speculates past the bounds check then
 * array_index_nospec() will clamp the index within the range of [0,
 * size)."

The above is part of the header for macro array_index_nospec() in
linux/nospec.h

Now, in this particular case, if intid evaluates to exactly VGIC_MAX_SPI
or to exaclty VGIC_MAX_PRIVATE, the array_index_nospec() macro ends up
returning VGIC_MAX_SPI - 1 or VGIC_MAX_PRIVATE - 1 respectively, instead
of VGIC_MAX_SPI or VGIC_MAX_PRIVATE, which, based on the original logic:

	/* SGIs and PPIs */
	if (intid <= VGIC_MAX_PRIVATE)
 		return &vcpu->arch.vgic_cpu.private_irqs[intid];

 	/* SPIs */
	if (intid <= VGIC_MAX_SPI)
 		return &kvm->arch.vgic.spis[intid - VGIC_NR_PRIVATE_IRQS];

are valid values for intid.

Fix this by calling array_index_nospec() macro with VGIC_MAX_PRIVATE + 1
and VGIC_MAX_SPI + 1 as arguments for its parameter size.

Fixes: 41b87599c743 ("KVM: arm/arm64: vgic: fix possible spectre-v1 in vgic_get_irq()")
Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva 
[dropped the SPI part which was fixed separately]
Signed-off-by: Marc Zyngier 
Signed-off-by: Greg Kroah-Hartman