Re: slab-out-of-bounds due to "KVM: Dynamically size memslot array based on number of used slots"

[Sean Christopherson]

On Fri, Mar 20, 2020 at 09:49:03AM -0400, Qian Cai wrote:
> 
> 
> > On Mar 20, 2020, at 12:34 AM, Sean Christopherson <sean.j.christopherson@xxxxxxxxx> wrote:
> > 
> > On Thu, Mar 19, 2020 at 11:59:23PM -0400, Qian Cai wrote:
> >> Reverted the linux-next commit 36947254e5f98 (âKVM: Dynamically size memslot array based on number of used slotsâ)
> >> fixed illegal slab object redzone accesses.
> >> 
> >> [6727.939776][ T1818] BUG: KASAN: slab-out-of-bounds in gfn_to_hva+0xc1/0x2b0 [kvm]
> >> search_memslots at include/linux/kvm_host.h:1035
> > 
> > Drat.  I'm guessing lru_slot is out of range after a memslot is deleted.
> > This should fix the issue, though it may not be the most proper fix, e.g.
> > it might be better to reset lru_slot when deleting a memslot.  I'll try and
> > reproduce tomorrow, unless you can confirm this does the trick.
> 
> It works fine.

Thanks!  I'll send a proper patch in a bit, tweaking a selftest to try and
hit this as well.