kernel.git/arch/arm/kvm, branch linux-4.11.y

KVM: arm/arm64: Handle possible NULL stage2 pud when ageing pages

2017-06-14T13:07:46Z

commit d6dbdd3c8558cad3b6d74cc357b408622d122331 upstream. Under memory pressure, we start ageing pages, which amounts to parsing the page tables. Since we don't want to allocate any extra level, we pass NULL for our private allocation cache. Which means that stage2_get_pud() is allowed to fail. This results in the following splat: [ 1520.409577] Unable to handle kernel NULL pointer dereference at virtual address 00000008 [ 1520.417741] pgd = ffff810f52fef000 [ 1520.421201] [00000008] *pgd=0000010f636c5003, *pud=0000010f56f48003, *pmd=0000000000000000 [ 1520.429546] Internal error: Oops: 96000006 [#1] PREEMPT SMP [ 1520.435156] Modules linked in: [ 1520.438246] CPU: 15 PID: 53550 Comm: qemu-system-aar Tainted: G W 4.12.0-rc4-00027-g1885c397eaec #7205 [ 1520.448705] Hardware name: FOXCONN R2-1221R-A4/C2U4N_MB, BIOS G31FB12A 10/26/2016 [ 1520.463726] task: ffff800ac5fb4e00 task.stack: ffff800ce04e0000 [ 1520.469666] PC is at stage2_get_pmd+0x34/0x110 [ 1520.474119] LR is at kvm_age_hva_handler+0x44/0xf0 [ 1520.478917] pc : [] lr : [] pstate: 40000145 [ 1520.486325] sp : ffff800ce04e33d0 [ 1520.489644] x29: ffff800ce04e33d0 x28: 0000000ffff40064 [ 1520.494967] x27: 0000ffff27e00000 x26: 0000000000000000 [ 1520.500289] x25: ffff81051ba65008 x24: 0000ffff40065000 [ 1520.505618] x23: 0000ffff40064000 x22: 0000000000000000 [ 1520.510947] x21: ffff810f52b20000 x20: 0000000000000000 [ 1520.516274] x19: 0000000058264000 x18: 0000000000000000 [ 1520.521603] x17: 0000ffffa6fe7438 x16: ffff000008278b70 [ 1520.526940] x15: 000028ccd8000000 x14: 0000000000000008 [ 1520.532264] x13: ffff7e0018298000 x12: 0000000000000002 [ 1520.537582] x11: ffff000009241b93 x10: 0000000000000940 [ 1520.542908] x9 : ffff0000092ef800 x8 : 0000000000000200 [ 1520.548229] x7 : ffff800ce04e36a8 x6 : 0000000000000000 [ 1520.553552] x5 : 0000000000000001 x4 : 0000000000000000 [ 1520.558873] x3 : 0000000000000000 x2 : 0000000000000008 [ 1520.571696] x1 : ffff000008fd5000 x0 : ffff0000080b149c [ 1520.577039] Process qemu-system-aar (pid: 53550, stack limit = 0xffff800ce04e0000) [...] [ 1521.510735] [] stage2_get_pmd+0x34/0x110 [ 1521.516221] [] kvm_age_hva_handler+0x44/0xf0 [ 1521.522054] [] handle_hva_to_gpa+0xb8/0xe8 [ 1521.527716] [] kvm_age_hva+0x44/0xf0 [ 1521.532854] [] kvm_mmu_notifier_clear_flush_young+0x70/0xc0 [ 1521.539992] [] __mmu_notifier_clear_flush_young+0x88/0xd0 [ 1521.546958] [] page_referenced_one+0xf0/0x188 [ 1521.552881] [] rmap_walk_anon+0xec/0x250 [ 1521.558370] [] rmap_walk+0x78/0xa0 [ 1521.563337] [] page_referenced+0x164/0x180 [ 1521.569002] [] shrink_active_list+0x178/0x3b8 [ 1521.574922] [] shrink_node_memcg+0x328/0x600 [ 1521.580758] [] shrink_node+0xc4/0x328 [ 1521.585986] [] do_try_to_free_pages+0xc0/0x340 [ 1521.592000] [] try_to_free_pages+0xcc/0x240 [...] The trivial fix is to handle this NULL pud value early, rather than dereferencing it blindly. Signed-off-by: Marc Zyngier Reviewed-by: Christoffer Dall Signed-off-by: Christoffer Dall Signed-off-by: Greg Kroah-Hartman

arm: KVM: Allow unaligned accesses at HYP

2017-06-14T13:07:39Z

commit 33b5c38852b29736f3b472dd095c9a18ec22746f upstream. We currently have the HSCTLR.A bit set, trapping unaligned accesses at HYP, but we're not really prepared to deal with it. Since the rest of the kernel is pretty happy about that, let's follow its example and set HSCTLR.A to zero. Modern CPUs don't really care. Signed-off-by: Marc Zyngier Signed-off-by: Christoffer Dall Signed-off-by: Greg Kroah-Hartman

kvm: arm/arm64: Force reading uncached stage2 PGD

2017-05-25T13:46:27Z

commit 2952a6070e07ebdd5896f1f5b861acad677caded upstream. Make sure we don't use a cached value of the KVM stage2 PGD while resetting the PGD. Cc: Marc Zyngier Signed-off-by: Suzuki K Poulose Reviewed-by: Christoffer Dall Signed-off-by: Christoffer Dall Signed-off-by: Greg Kroah-Hartman

kvm: arm/arm64: Fix use after free of stage2 page table

2017-05-25T13:46:27Z

commit 0c428a6a9256fcd66817e12db32a50b405ed2e5c upstream. We yield the kvm->mmu_lock occassionaly while performing an operation (e.g, unmap or permission changes) on a large area of stage2 mappings. However this could possibly cause another thread to clear and free up the stage2 page tables while we were waiting for regaining the lock and thus the original thread could end up in accessing memory that was freed. This patch fixes the problem by making sure that the stage2 pagetable is still valid after we regain the lock. The fact that mmu_notifer->release() could be called twice (via __mmu_notifier_release and mmu_notifier_unregsister) enhances the possibility of hitting this race where there are two threads trying to unmap the entire guest shadow pages. While at it, cleanup the redudant checks around cond_resched_lock in stage2_wp_range(), as cond_resched_lock already does the same checks. Cc: Mark Rutland Cc: Radim Krčmář Cc: andreyknvl@google.com Cc: Paolo Bonzini Acked-by: Marc Zyngier Signed-off-by: Suzuki K Poulose Reviewed-by: Christoffer Dall Signed-off-by: Christoffer Dall Signed-off-by: Greg Kroah-Hartman

kvm: arm/arm64: Fix race in resetting stage2 PGD

2017-05-25T13:46:27Z

commit 6c0d706b563af732adb094c5bf807437e8963e84 upstream. In kvm_free_stage2_pgd() we check the stage2 PGD before holding the lock and proceed to take the lock if it is valid. And we unmap the page tables, followed by releasing the lock. We reset the PGD only after dropping this lock, which could cause a race condition where another thread waiting on or even holding the lock, could potentially see that the PGD is still valid and proceed to perform a stage2 operation and later encounter a NULL PGD. [223090.242280] Unable to handle kernel NULL pointer dereference at virtual address 00000040 [223090.262330] PC is at unmap_stage2_range+0x8c/0x428 [223090.262332] LR is at kvm_unmap_hva_handler+0x2c/0x3c [223090.262531] Call trace: [223090.262533] [] unmap_stage2_range+0x8c/0x428 [223090.262535] [] kvm_unmap_hva_handler+0x2c/0x3c [223090.262537] [] handle_hva_to_gpa+0xb0/0x104 [223090.262539] [] kvm_unmap_hva+0x5c/0xbc [223090.262543] [] kvm_mmu_notifier_invalidate_page+0x50/0x8c [223090.262547] [] __mmu_notifier_invalidate_page+0x5c/0x84 [223090.262551] [] try_to_unmap_one+0x1d0/0x4a0 [223090.262553] [] rmap_walk+0x1cc/0x2e0 [223090.262555] [] try_to_unmap+0x74/0xa4 [223090.262557] [] migrate_pages+0x31c/0x5ac [223090.262561] [] compact_zone+0x3fc/0x7ac [223090.262563] [] compact_zone_order+0x94/0xb0 [223090.262564] [] try_to_compact_pages+0x108/0x290 [223090.262569] [] __alloc_pages_direct_compact+0x70/0x1ac [223090.262571] [] __alloc_pages_nodemask+0x434/0x9f4 [223090.262572] [] alloc_pages_vma+0x230/0x254 [223090.262574] [] do_huge_pmd_anonymous_page+0x114/0x538 [223090.262576] [] handle_mm_fault+0xd40/0x17a4 [223090.262577] [] __get_user_pages+0x12c/0x36c [223090.262578] [] get_user_pages_unlocked+0xa4/0x1b8 [223090.262579] [] __gfn_to_pfn_memslot+0x280/0x31c [223090.262580] [] gfn_to_pfn_prot+0x4c/0x5c [223090.262582] [] kvm_handle_guest_abort+0x240/0x774 [223090.262584] [] handle_exit+0x11c/0x1ac [223090.262586] [] kvm_arch_vcpu_ioctl_run+0x31c/0x648 [223090.262587] [] kvm_vcpu_ioctl+0x378/0x768 [223090.262590] [] do_vfs_ioctl+0x324/0x5a4 [223090.262591] [] SyS_ioctl+0x90/0xa4 [223090.262595] [] el0_svc_naked+0x38/0x3c This patch moves the stage2 PGD manipulation under the lock. Reported-by: Alexander Graf Cc: Mark Rutland Cc: Marc Zyngier Cc: Paolo Bonzini Cc: Radim Krčmář Reviewed-by: Christoffer Dall Reviewed-by: Marc Zyngier Signed-off-by: Suzuki K Poulose Signed-off-by: Christoffer Dall Signed-off-by: Greg Kroah-Hartman

KVM: arm: plug potential guest hardware debug leakage

2017-05-25T13:46:24Z

commit 661e6b02b5aa82db31897f36e96324b77450fd7a upstream. Hardware debugging in guests is not intercepted currently, it means that a malicious guest can bring down the entire machine by writing to the debug registers. This patch enable trapping of all debug registers, preventing the guests to access the debug registers. This includes access to the debug mode(DBGDSCR) in the guest world all the time which could otherwise mess with the host state. Reads return 0 and writes are ignored (RAZ_WI). The result is the guest cannot detect any working hardware based debug support. As debug exceptions are still routed to the guest normal debug using software based breakpoints still works. To support debugging using hardware registers we need to implement a debug register aware world switch as well as special trapping for registers that may affect the host state. Signed-off-by: Zhichao Huang Signed-off-by: Alex Bennée Reviewed-by: Christoffer Dall Signed-off-by: Christoffer Dall Signed-off-by: Greg Kroah-Hartman

arm: KVM: Do not use stack-protector to compile HYP code

2017-05-25T13:46:23Z

commit 501ad27c67ed0b90df465f23d33e9aed64058a47 upstream. We like living dangerously. Nothing explicitely forbids stack-protector to be used in the HYP code, while distributions routinely compile their kernel with it. We're just lucky that no code actually triggers the instrumentation. Let's not try our luck for much longer, and disable stack-protector for code living at HYP. Signed-off-by: Marc Zyngier Acked-by: Christoffer Dall Signed-off-by: Christoffer Dall Signed-off-by: Greg Kroah-Hartman

KVM: arm/arm64: fix races in kvm_psci_vcpu_on

2017-05-20T12:49:42Z

commit 6c7a5dce22b3f3cc44be098e2837fa6797edb8b8 upstream. Fix potential races in kvm_psci_vcpu_on() by taking the kvm->lock mutex. In general, it's a bad idea to allow more than one PSCI_CPU_ON to process the same target VCPU at the same time. One such problem that may arise is that one PSCI_CPU_ON could be resetting the target vcpu, which fills the entire sys_regs array with a temporary value including the MPIDR register, while another looks up the VCPU based on the MPIDR value, resulting in no target VCPU found. Resolves both races found with the kvm-unit-tests/arm/psci unit test. Reviewed-by: Marc Zyngier Reviewed-by: Christoffer Dall Reported-by: Levente Kurusa Suggested-by: Christoffer Dall Signed-off-by: Andrew Jones Signed-off-by: Christoffer Dall Signed-off-by: Greg Kroah-Hartman

KVM: arm64: Ensure LRs are clear when they should be

2017-04-04T12:33:58Z

We currently have some code to clear the list registers on GICv3, but we never call this code, because the caller got nuked when removing the old vgic. We also used to have a similar GICv2 part, but that got lost in the process too. Let's reintroduce the logic for GICv2 and call the logic when we initialize the use of hypervisors on the CPU, for example when first loading KVM or when exiting a low power state. Reviewed-by: Marc Zyngier Signed-off-by: Christoffer Dall Signed-off-by: Marc Zyngier

kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd

2017-04-04T12:33:50Z

In kvm_free_stage2_pgd() we don't hold the kvm->mmu_lock while calling unmap_stage2_range() on the entire memory range for the guest. This could cause problems with other callers (e.g, munmap on a memslot) trying to unmap a range. And since we have to unmap the entire Guest memory range holding a spinlock, make sure we yield the lock if necessary, after we unmap each PUD range. Fixes: commit d5d8184d35c9 ("KVM: ARM: Memory virtualization setup") Cc: stable@vger.kernel.org # v3.10+ Cc: Paolo Bonzini Cc: Marc Zyngier Cc: Christoffer Dall Cc: Mark Rutland Signed-off-by: Suzuki K Poulose [ Avoid vCPU starvation and lockup detector warnings ] Signed-off-by: Marc Zyngier Signed-off-by: Suzuki K Poulose Signed-off-by: Christoffer Dall