KVM: arm64: vgic-v3: Undo assignment on iodev registration failure

vgic_register_redist_iodev() assigns a redistributor region and base
address to the vCPU before adding its iodev to the MMIO bus. However, the
region's free_index is advanced only after registration succeeds.

If kvm_io_bus_register_dev() fails, the vCPU retains the assignment while
free_index still identifies the same slot as free. A later registration can
therefore reuse a slot that remains assigned to the vCPU.

Reserve the slot before registering its iodev. The caller holds slots_lock,
so a registration failure cannot race with a later assignment. Undo the
reservation and clear the cached assignment on failure.

Fixes: dbd9733ab674 ("KVM: arm/arm64: Replace the single rdist region by a list")
Cc: stable@vger.kernel.org
Assisted-by: Codex:gpt-5.6-sol
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Tested-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20260831081005.41346-2-kmehltretter@gmail.com
[maz: moved helper into the sole caller]
Signed-off-by: Marc Zyngier <maz@kernel.org>

0 files changed, 0 insertions, 0 deletions