From f8c1b85b2523da59c8c03ea94e9d0fac04155943 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 1 Jun 2016 14:09:22 +0200 Subject: [PATCH] KVM: x86: avoid vmalloc(0) in the KVM_SET_CPUID MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This causes an ugly dmesg splat. Beautified syzkaller testcase: #include #include #include #include #include long r[8]; int main() { struct kvm_irq_routing ir = { 0 }; r[2] = open("/dev/kvm", O_RDWR); r[3] = ioctl(r[2], KVM_CREATE_VM, 0); r[4] = ioctl(r[3], KVM_SET_GSI_ROUTING, &ir); return 0; } Reported-by: Dmitry Vyukov Signed-off-by: Paolo Bonzini Signed-off-by: Radim Krčmář --- virt/kvm/kvm_main.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 37af23052470..02e98f3131bd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2935,7 +2935,7 @@ static long kvm_vm_ioctl(struct file *filp, case KVM_SET_GSI_ROUTING: { struct kvm_irq_routing routing; struct kvm_irq_routing __user *urouting; - struct kvm_irq_routing_entry *entries; + struct kvm_irq_routing_entry *entries = NULL; r = -EFAULT; if (copy_from_user(&routing, argp, sizeof(routing))) @@ -2945,15 +2945,17 @@ static long kvm_vm_ioctl(struct file *filp, goto out; if (routing.flags) goto out; - r = -ENOMEM; - entries = vmalloc(routing.nr * sizeof(*entries)); - if (!entries) - goto out; - r = -EFAULT; - urouting = argp; - if (copy_from_user(entries, urouting->entries, - routing.nr * sizeof(*entries))) - goto out_free_irq_routing; + if (routing.nr) { + r = -ENOMEM; + entries = vmalloc(routing.nr * sizeof(*entries)); + if (!entries) + goto out; + r = -EFAULT; + urouting = argp; + if (copy_from_user(entries, urouting->entries, + routing.nr * sizeof(*entries))) + goto out_free_irq_routing; + } r = kvm_set_irq_routing(kvm, entries, routing.nr, routing.flags); out_free_irq_routing: -- 2.20.1