vfio/cdx: Consolidate MSI configured state onto cdx_irqs

struct vfio_cdx_device carries three fields that track whether MSI has
been configured: vdev->cdx_irqs (the allocated vector array), vdev->
m

vfio/cdx: Consolidate MSI configured state onto cdx_irqs

struct vfio_cdx_device carries three fields that track whether MSI has
been configured: vdev->cdx_irqs (the allocated vector array), vdev->
msi_count (the array length), and vdev->config_msi (a boolean flag).
The three are set together when vfio_cdx_msi_enable() succeeds and
cleared together by vfio_cdx_msi_disable(). However, the error paths
in vfio_cdx_msi_enable() free the cdx_irqs allocation on failure
without resetting the pointer, leaving it stale and skewed from the
other two fields until the next enable call overwrites it.

Clear vdev->cdx_irqs to NULL alongside the kfree() in both error paths
so the pointer consistently reflects the configured state. With that
invariant restored and access to the MSI state serialized by
cdx_irqs_lock, vdev->config_msi is fully redundant with
(vdev->cdx_irqs != NULL). Drop the config_msi field and switch all
readers to test cdx_irqs directly.

Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Alex Williamson <alex.williamson@nvidia.com>
Acked-by: Nikhil Agarwal <nikhil.agarwal@amd.com>
Link: https://lore.kernel.org/r/20260417202800.88287-4-alex.williamson@nvidia.com
Signed-off-by: Alex Williamson <alex@shazbot.org>

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vfio/cdx: Serialize VFIO_DEVICE_SET_IRQS with a per-device mutex

vfio_cdx_set_msi_trigger() reads vdev->config_msi and operates on the
vdev->cdx_irqs array based on its value, but provides no serial

vfio/cdx: Serialize VFIO_DEVICE_SET_IRQS with a per-device mutex

vfio_cdx_set_msi_trigger() reads vdev->config_msi and operates on the
vdev->cdx_irqs array based on its value, but provides no serialization
against concurrent VFIO_DEVICE_SET_IRQS ioctls. Two callers can race
such that one observes config_msi as set while another clears it and
frees cdx_irqs via vfio_cdx_msi_disable(), resulting in a use-after-free
of the cdx_irqs array.

Add a cdx_irqs_lock mutex to struct vfio_cdx_device and acquire it in
vfio_cdx_set_msi_trigger(), which is the single chokepoint through
which all updates to config_msi, cdx_irqs, and msi_count flow, covering
both the ioctl path and the close-device cleanup path. This keeps the
test of config_msi atomic with the subsequent enable, disable, or
trigger operations.

Drop the pre-call !cdx_irqs test from vfio_cdx_irqs_cleanup() as part
of this change: the optimization it provided is redundant with the
!config_msi early-return inside vfio_cdx_msi_disable(), and leaving the
test in place would be an unsynchronized read of state the new lock is
meant to protect.

Fixes: 848e447e000c ("vfio/cdx: add interrupt support")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Alex Williamson <alex.williamson@nvidia.com>
Acked-by: Nikhil Agarwal <nikhil.agarwal@amd.com>
Link: https://lore.kernel.org/r/20260417202800.88287-3-alex.williamson@nvidia.com
Signed-off-by: Alex Williamson <alex@shazbot.org>

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vfio/cdx: Fix NULL pointer dereference in interrupt trigger path

Add validation to ensure MSI is configured before accessing cdx_irqs
array in vfio_cdx_set_msi_trigger(). Without this check, userspa

vfio/cdx: Fix NULL pointer dereference in interrupt trigger path

Add validation to ensure MSI is configured before accessing cdx_irqs
array in vfio_cdx_set_msi_trigger(). Without this check, userspace
can trigger a NULL pointer dereference by calling VFIO_DEVICE_SET_IRQS
with VFIO_IRQ_SET_DATA_BOOL or VFIO_IRQ_SET_DATA_NONE flags before
ever setting up interrupts via VFIO_IRQ_SET_DATA_EVENTFD.

The vfio_cdx_msi_enable() function allocates the cdx_irqs array and
sets config_msi to 1 only when called through the EVENTFD path. The
trigger loop (for DATA_BOOL/DATA_NONE) assumed this had already been
done, but there was no enforcement of this call ordering.

This matches the protection used in the PCI VFIO driver where
vfio_pci_set_msi_trigger() checks irq_is() before the trigger loop.

Fixes: 848e447e000c ("vfio/cdx: add interrupt support")
Cc: stable@vger.kernel.org
Signed-off-by: Prasanna Kumar T S M <ptsm@linux.microsoft.com>
Acked-by: Nipun Gupta <nipun.gupta@amd.com>
Signed-off-by: Alex Williamson <alex.williamson@nvidia.com>
Acked-by: Nikhil Agarwal <nikhil.agarwal@amd.com>
Link: https://lore.kernel.org/r/20260417202800.88287-2-alex.williamson@nvidia.com
Signed-off-by: Alex Williamson <alex@shazbot.org>

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