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KVM: x86: avoid vmalloc(0) in the KVM_SET_CPUID

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This causes an ugly dmesg splat.  Beautified syzkaller testcase:

    #include <unistd.h>
    #include <sys/syscall.h>
    #include <sys/ioctl.h>
    #include <fcntl.h>
    #include <linux/kvm.h>

    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 <dvyukov@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Paolo Bonzini 2016-06-01 14:09:22 +02:00 committed by Radim Krčmář
parent c622a3c21e
commit f8c1b85b25
1 changed files with 12 additions and 10 deletions
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22
virt/kvm/kvm_main.c
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@ -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: