6.6-stable review patch. If anyone has any objections, please let me know.
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From: Raghavendra Rao Ananta rananta@google.com
commit 38d7aacca09230fdb98a34194fec2af597e8e20d upstream.
Improper use of userspace_irqchip_in_use led to syzbot hitting the following WARN_ON() in kvm_timer_update_irq():
WARNING: CPU: 0 PID: 3281 at arch/arm64/kvm/arch_timer.c:459 kvm_timer_update_irq+0x21c/0x394 Call trace: kvm_timer_update_irq+0x21c/0x394 arch/arm64/kvm/arch_timer.c:459 kvm_timer_vcpu_reset+0x158/0x684 arch/arm64/kvm/arch_timer.c:968 kvm_reset_vcpu+0x3b4/0x560 arch/arm64/kvm/reset.c:264 kvm_vcpu_set_target arch/arm64/kvm/arm.c:1553 [inline] kvm_arch_vcpu_ioctl_vcpu_init arch/arm64/kvm/arm.c:1573 [inline] kvm_arch_vcpu_ioctl+0x112c/0x1b3c arch/arm64/kvm/arm.c:1695 kvm_vcpu_ioctl+0x4ec/0xf74 virt/kvm/kvm_main.c:4658 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __arm64_sys_ioctl+0x108/0x184 fs/ioctl.c:893 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x78/0x1b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0xe8/0x1b0 arch/arm64/kernel/syscall.c:132 do_el0_svc+0x40/0x50 arch/arm64/kernel/syscall.c:151 el0_svc+0x54/0x14c arch/arm64/kernel/entry-common.c:712 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
The following sequence led to the scenario: - Userspace creates a VM and a vCPU. - The vCPU is initialized with KVM_ARM_VCPU_PMU_V3 during KVM_ARM_VCPU_INIT. - Without any other setup, such as vGIC or vPMU, userspace issues KVM_RUN on the vCPU. Since the vPMU is requested, but not setup, kvm_arm_pmu_v3_enable() fails in kvm_arch_vcpu_run_pid_change(). As a result, KVM_RUN returns after enabling the timer, but before incrementing 'userspace_irqchip_in_use': kvm_arch_vcpu_run_pid_change() ret = kvm_arm_pmu_v3_enable() if (!vcpu->arch.pmu.created) return -EINVAL; if (ret) return ret; [...] if (!irqchip_in_kernel(kvm)) static_branch_inc(&userspace_irqchip_in_use); - Userspace ignores the error and issues KVM_ARM_VCPU_INIT again. Since the timer is already enabled, control moves through the following flow, ultimately hitting the WARN_ON(): kvm_timer_vcpu_reset() if (timer->enabled) kvm_timer_update_irq() if (!userspace_irqchip()) ret = kvm_vgic_inject_irq() ret = vgic_lazy_init() if (unlikely(!vgic_initialized(kvm))) if (kvm->arch.vgic.vgic_model != KVM_DEV_TYPE_ARM_VGIC_V2) return -EBUSY; WARN_ON(ret);
Theoretically, since userspace_irqchip_in_use's functionality can be simply replaced by '!irqchip_in_kernel()', get rid of the static key to avoid the mismanagement, which also helps with the syzbot issue.
Cc: stable@vger.kernel.org Reported-by: syzbot syzkaller@googlegroups.com Suggested-by: Marc Zyngier maz@kernel.org Signed-off-by: Raghavendra Rao Ananta rananta@google.com Signed-off-by: Oliver Upton oliver.upton@linux.dev Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/include/asm/kvm_host.h | 2 -- arch/arm64/kvm/arch_timer.c | 3 +-- arch/arm64/kvm/arm.c | 18 +++--------------- 3 files changed, 4 insertions(+), 19 deletions(-)
--- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -72,8 +72,6 @@ enum kvm_mode kvm_get_mode(void); static inline enum kvm_mode kvm_get_mode(void) { return KVM_MODE_NONE; }; #endif
-DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use); - extern unsigned int __ro_after_init kvm_sve_max_vl; int __init kvm_arm_init_sve(void);
--- a/arch/arm64/kvm/arch_timer.c +++ b/arch/arm64/kvm/arch_timer.c @@ -206,8 +206,7 @@ void get_timer_map(struct kvm_vcpu *vcpu
static inline bool userspace_irqchip(struct kvm *kvm) { - return static_branch_unlikely(&userspace_irqchip_in_use) && - unlikely(!irqchip_in_kernel(kvm)); + return unlikely(!irqchip_in_kernel(kvm)); }
static void soft_timer_start(struct hrtimer *hrt, u64 ns) --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -57,7 +57,6 @@ DECLARE_KVM_NVHE_PER_CPU(struct kvm_cpu_ static bool vgic_present, kvm_arm_initialised;
static DEFINE_PER_CPU(unsigned char, kvm_hyp_initialized); -DEFINE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
bool is_kvm_arm_initialised(void) { @@ -401,9 +400,6 @@ void kvm_arch_vcpu_postcreate(struct kvm
void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu) { - if (vcpu_has_run_once(vcpu) && unlikely(!irqchip_in_kernel(vcpu->kvm))) - static_branch_dec(&userspace_irqchip_in_use); - kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_cache); kvm_timer_vcpu_terminate(vcpu); kvm_pmu_vcpu_destroy(vcpu); @@ -627,14 +623,6 @@ int kvm_arch_vcpu_run_pid_change(struct return ret; }
- if (!irqchip_in_kernel(kvm)) { - /* - * Tell the rest of the code that there are userspace irqchip - * VMs in the wild. - */ - static_branch_inc(&userspace_irqchip_in_use); - } - /* * Initialize traps for protected VMs. * NOTE: Move to run in EL2 directly, rather than via a hypercall, once @@ -856,7 +844,7 @@ static bool kvm_vcpu_exit_request(struct * state gets updated in kvm_timer_update_run and * kvm_pmu_update_run below). */ - if (static_branch_unlikely(&userspace_irqchip_in_use)) { + if (unlikely(!irqchip_in_kernel(vcpu->kvm))) { if (kvm_timer_should_notify_user(vcpu) || kvm_pmu_should_notify_user(vcpu)) { *ret = -EINTR; @@ -975,7 +963,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v vcpu->mode = OUTSIDE_GUEST_MODE; isb(); /* Ensure work in x_flush_hwstate is committed */ kvm_pmu_sync_hwstate(vcpu); - if (static_branch_unlikely(&userspace_irqchip_in_use)) + if (unlikely(!irqchip_in_kernel(vcpu->kvm))) kvm_timer_sync_user(vcpu); kvm_vgic_sync_hwstate(vcpu); local_irq_enable(); @@ -1021,7 +1009,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v * we don't want vtimer interrupts to race with syncing the * timer virtual interrupt state. */ - if (static_branch_unlikely(&userspace_irqchip_in_use)) + if (unlikely(!irqchip_in_kernel(vcpu->kvm))) kvm_timer_sync_user(vcpu);
kvm_arch_vcpu_ctxsync_fp(vcpu);