[PATCH v2 0/2] arm_ffa, KVM: Fix FF-A emad offset calculations

[Sebastian Ene <sebastianene@google.com>]

Hi all,

This series fixes the Endpoint Memory Access Descriptor (EMAD) offset calculations
and adds the necessary bounds checks for both the core FF-A driver and the pKVM
hypervisor.

Prior to FF-A version 1.1, the memory region header didn't specify an explicit offset
for the EMADs, leading to the assumption that they immediately follow the header.
However, from v1.1 onwards, the specification dictates using the `ep_mem_offset` field
to determine the start of the memory access array.

The patches in this series address this by:
1. Updating the core `arm_ffa` firmware driver to correctly calculate the descriptor
   offset using `ep_mem_offset` rather than defaulting to `sizeof(struct ffa_mem_region)`.
   It also introduces bounds checking against `max_fragsize`.
2. Enhancing the pKVM hypervisor validation logic to no longer strictly enforce that
   the descriptor strictly follows the header, aligning it with the driver behavior
   and the FF-A specification, while also ensuring the offset falls within the mailbox
   buffer bounds.

Changes since v1:
- For pKVM, removed the strict placement enforcement for `ep_mem_offset` as it is not
  compliant with the spec, and avoids making assumptions about the driver's memory
  layout.

Link to v1: https://lore.kernel.org/all/ae9KN9nkOgDYJcGP@google.com/T/#t

Sebastian Ene (2):
  firmware: arm_ffa: Fix Endpoint Memory Access Descriptor offset
    calculation
  KVM: arm64: Validate the offset to the mem access descriptor

 arch/arm64/kvm/hyp/nvhe/ffa.c     | 24 ++++++++++++++++++------
 drivers/firmware/arm_ffa/driver.c | 14 ++++++++++----
 include/linux/arm_ffa.h           |  2 +-
 3 files changed, 29 insertions(+), 11 deletions(-)

--
2.54.0.545.g6539524ca2-goog