David Gibson [off-list ref] writes:

On Wed, Nov 29, 2017 at 11:38:22AM -0500, Serhii Popovych wrote:

quoted

It is possible to trigger use after free during HPT resize
causing host kernel to crash. More details and analysis of
the problem can be found in change with corresponding subject
(KVM: PPC: Book3S HV: Fix use after free in case of multiple
resize requests).

We need some changes to prepare for the fix, especially
make ->error in HPT resize instance single point for
tracking allocation state, improve kvmppc_allocate_hpt()
and kvmppc_free_hpt() so they can be used more safely.

See individual commit description message to get more
information on changes presented.

I spoke with Paul Mackerras about these patches on IRC today.  We want
this as a fix, ASAP, in 4.15.  However, he's uncomfortable with
pushing some of extra cleanups which aren't necessary for the bug fix
this late for 4.15, and was having trouble following what was the core
of the fix.  He was also nervous about the addition of more BUG_ON()s.

As was I.

To avoid the round trip to Ukraine time and back, I've made revised
versions of patches 1 & 3 which should apply standalone, replaced the
BUG_ON()s with WARN_ON()s

Thanks.

cheers