Re: [PATCH] mshv: Fix infinite fault loop on permission-denied GPA intercepts

[Wei Liu <wei.liu@kernel.org>]

On Thu, Apr 02, 2026 at 03:44:58PM +0000, Anirudh Rayabharam wrote:
> On Tue, Mar 24, 2026 at 11:57:40PM +0000, Stanislav Kinsburskii wrote:
> > Prevent infinite fault loops when guests access memory regions without
> > proper permissions. Currently, mshv_handle_gpa_intercept() attempts to
> > remap pages for all faults on movable memory regions, regardless of
> > whether the access type is permitted. When a guest writes to a read-only
> > region, the remap succeeds but the region remains read-only, causing
> > immediate re-fault and spinning the vCPU indefinitely.
> > 
> > Validate intercept access type against region permissions before
> > attempting remaps. Reject writes to non-writable regions and executes to
> > non-executable regions early, returning false to let the VMM handle the
> > intercept appropriately.
> > 
> > This also closes a potential DoS vector where malicious guests could
> > intentionally trigger these fault loops to consume host resources.
> > 
> > Fixes: b9a66cd5ccbb ("mshv: Add support for movable memory regions")
> > Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
> > ---
> >  drivers/hv/mshv_root_main.c |   15 ++++++++++++---
> >  include/hyperv/hvgdk_mini.h |    6 ++++++
> >  include/hyperv/hvhdk.h      |    4 ++--
> >  3 files changed, 20 insertions(+), 5 deletions(-)
> 
> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
> 

Applied to hyperv-fixes.