On Tue, Sep 01, 2020 at 06:25:42PM +0200, Vitaly Kuznetsov wrote:
> Rustam Kovhaev <[email protected]> writes:
>
> > when kmalloc() fails in kvm_io_bus_unregister_dev(), before removing
> > the bus, we should iterate over all other devices linked to it and call
> > kvm_iodevice_destructor() for them
> >
> > Reported-and-tested-by:
> > [email protected]
> > Link: https://syzkaller.appspot.com/bug?extid=f196caa45793d6374707
> > Signed-off-by: Rustam Kovhaev <[email protected]>
> > ---
> > virt/kvm/kvm_main.c | 7 ++++++-
> > 1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 67cd0b88a6b6..646aa7b82548 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -4332,7 +4332,7 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum
> > kvm_bus bus_idx, gpa_t addr,
> > void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
> > struct kvm_io_device *dev)
> > {
> > - int i;
> > + int i, j;
> > struct kvm_io_bus *new_bus, *bus;
> >
> > bus = kvm_get_bus(kvm, bus_idx);
> > @@ -4351,6 +4351,11 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum
> > kvm_bus bus_idx,
> > GFP_KERNEL_ACCOUNT);
> > if (!new_bus) {
> ^^^ redundant space
>
> > pr_err("kvm: failed to shrink bus, removing it completely\n");
> > + for (j = 0; j < bus->dev_count; j++) {
> > + if (j == i)
> > + continue;
> > + kvm_iodevice_destructor(bus->range[j].dev);
> > + }
> > goto broken;
>
> The name of the label is really misleading (as it is not actually a
> failure path), I'd even suggest we get rid of this goto completely,
> something like
>
> new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
> GFP_KERNEL_ACCOUNT);
> if (new_bus) {
> memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct
> kvm_io_range));
> new_bus->dev_count--;
> memcpy(new_bus->range + i, bus->range + i + 1,
> (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
> } else {
> pr_err("kvm: failed to shrink bus, removing it completely\n");
> for (j = 0; j < bus->dev_count; j++) {
> if (j == i)
> continue;
> kvm_iodevice_destructor(bus->range[j].dev);
> }
>
> rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
> synchronize_srcu_expedited(&kvm->srcu);
> kfree(bus);
> return;
>
>
> > }
>
> None of the above should block the fix IMO, so:
>
> Reviewed-by: Vitaly Kuznetsov <[email protected]>
>
> --
> Vitaly
>
hi Vitaly, thank you for the review! i'll send the new patch
