On 07/09/20 20:55, 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

Fixes: 90db10434b16 ("KVM: kvm_io_bus_unregister_dev() should never fail") Cc: stable@vger.kernel.org Reported-and-tested-by: syzbot+f196caa45793d6374707@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?extid=f196caa45793d6374707 Signed-off-by: Rustam Kovhaev rkovhaev@gmail.com Reviewed-by: Vitaly Kuznetsov vkuznets@redhat.com

---

v2:

• remove redundant whitespace
• remove goto statement and use if/else
• add Fixes tag

---

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));
  

• 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");

• 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);

Queued, thanks.

I am currently on leave so I am going through the patches and queuing them, but I will only push kvm/next and kvm/queue next week. kvm/master patches will be sent to Linus for the next -rc though.

Paolo