KVM: PPC: Fix kvm_arch_vcpu_ioctl vcpu_load leak

vcpu_put is not called if the user copy fails. This can result in preempt
notifier corruption and crashes, among other issues.

Fixes: b3cebfe8c1ca ("KVM: PPC: Move vcpu_load/vcpu_put down to each ioctl case in kvm_arch_vcpu_ioctl")
Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210716024310.164448-2-npiggin@gmail.com

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index be33b53..b4e6f70 100644 (file)
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -2048,9 +2048,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
        {
                struct kvm_enable_cap cap;
                r = -EFAULT;
-               vcpu_load(vcpu);
                if (copy_from_user(&cap, argp, sizeof(cap)))
                        goto out;
+               vcpu_load(vcpu);
                r = kvm_vcpu_ioctl_enable_cap(vcpu, &cap);
                vcpu_put(vcpu);
                break;
@@ -2074,9 +2074,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
        case KVM_DIRTY_TLB: {
                struct kvm_dirty_tlb dirty;
                r = -EFAULT;
-               vcpu_load(vcpu);
                if (copy_from_user(&dirty, argp, sizeof(dirty)))
                        goto out;
+               vcpu_load(vcpu);
                r = kvm_vcpu_ioctl_dirty_tlb(vcpu, &dirty);
                vcpu_put(vcpu);
                break;