iommu: Fix crash in report_iommu_fault()

commit df4bf3f
Author: Fedor Pchelkin <[email protected]>
Date: Wed Apr 9 00:33:41 2025 +0300

    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: 6aa63a4 ("iommu: Sort out domain user data")
    Signed-off-by: Fedor Pchelkin <[email protected]>
    Reviewed-by: Kevin Tian <[email protected]>
    Reviewed-by: Jason Gunthorpe <[email protected]>
    Link: https://lore.kernel.org/r/[email protected]
    Signed-off-by: Joerg Roedel <[email protected]>

(cherry picked from commit df4bf3f)
Signed-off-by: Jerry Snitselaar <[email protected]>
Upstream-Status: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
JIRA: https://issues.redhat.com/browse/RHEL-89891

Author: snits

drivers/iommu/iommu.c

@@ -2718,7 +2718,8 @@ int report_iommu_fault(struct iommu_domain *domain, struct device *dev,
 	 * if upper layers showed interest and installed a fault handler,
 	 * invoke it.
 	 */
-	if (domain->handler)
+	if (domain->cookie_type == IOMMU_COOKIE_FAULT_HANDLER &&
+	    domain->handler)
 		ret = domain->handler(domain, dev, iova, flags,
 						domain->handler_token);