Hi,
On 9/2/20 17:57, Rustam Kovhaev wrote:
> 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]>
> Reviewed-by: Vitaly Kuznetsov <[email protected]>
I think it's worthwhile to add a Fixes tag for this, too.
Please, see more comments below...
> ---
> v2:
> - remove redundant whitespace
> - remove goto statement and use if/else
> ---
> virt/kvm/kvm_main.c | 21 ++++++++++++---------
> 1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 67cd0b88a6b6..cf88233b819a 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);
> @@ -4349,17 +4349,20 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum
> kvm_bus bus_idx,
>
> new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
> GFP_KERNEL_ACCOUNT);
> - if (!new_bus) {
> + if (new_bus) {
> + memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct
> kvm_io_range));
^^^
It seems that you can use struct_size() here (see the allocation code above)...
> + new_bus->dev_count--;
> + memcpy(new_bus->range + i, bus->range + i + 1,
> + (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
^^^
...and, if possible, you can also use flex_array_size() here.
Thanks
--
Gustavo
> + } else {
> pr_err("kvm: failed to shrink bus, removing it completely\n");
> - goto broken;
> + for (j = 0; j < bus->dev_count; j++) {
> + if (j == i)
> + continue;
> + kvm_iodevice_destructor(bus->range[j].dev);
> + }
> }
>
> - 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));
> -
> -broken:
> rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
> synchronize_srcu_expedited(&kvm->srcu);
> kfree(bus);
>
