iommu: Fix crash in report_iommu_fault()

iommu: Fix crash in report_iommu_fault()

The following crash is observed while handling an IOMMU fault with a
recent kernel:

kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
BUG: unable to handle page fault for address: ffff8c708299f700
PGD 19ee01067 P4D 19ee01067 PUD 101c10063 PMD 80000001028001e3
Oops: Oops: 0011 [#1] SMP NOPTI
CPU: 4 UID: 0 PID: 139 Comm: irq/25-AMD-Vi Not tainted 6.15.0-rc1+ #20 PREEMPT(lazy)
Hardware name: LENOVO 21D0/LNVNB161216, BIOS J6CN50WW 09/27/2024
RIP: 0010:0xffff8c708299f700
Call Trace:
 <TASK>
 ? report_iommu_fault+0x78/0xd3
 ? amd_iommu_report_page_fault+0x91/0x150
 ? amd_iommu_int_thread+0x77/0x180
 ? __pfx_irq_thread_fn+0x10/0x10
 ? irq_thread_fn+0x23/0x60
 ? irq_thread+0xf9/0x1e0
 ? __pfx_irq_thread_dtor+0x10/0x10
 ? __pfx_irq_thread+0x10/0x10
 ? kthread+0xfc/0x240
 ? __pfx_kthread+0x10/0x10
 ? ret_from_fork+0x34/0x50
 ? __pfx_kthread+0x10/0x10
 ? ret_from_fork_asm+0x1a/0x30
 </TASK>

report_iommu_fault() checks for an installed handler comparing the
corresponding field to NULL. It can (and could before) be called for a
domain with a different cookie type - IOMMU_COOKIE_DMA_IOVA, specifically.
Cookie is represented as a union so we may end up with a garbage value
treated there if this happens for a domain with another cookie type.

Formerly there were two exclusive cookie types in the union.
IOMMU_DOMAIN_SVA has a dedicated iommu_report_device_fault().

Call the fault handler only if the passed domain has a required cookie
type.

Found by Linux Verification Center (linuxtesting.org).

Fixes: 6aa63a4ec947 ("iommu: Sort out domain user data")
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20250408213342.285955-1-pchelkin@ispras.ru
Signed-off-by: Joerg Roedel <jroedel@suse.de>