iommu/amd: Bounds-check devid in __rlookup_amd_iommu()

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Summary

CVECVE-2026-53283
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-26 20:17:20 UTC
Updated2026-06-26 20:17:20 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: iommu/amd: Bounds-check devid in __rlookup_amd_iommu() iommu_device_register() walks every device on the PCI bus via bus_for_each_dev() and calls amd_iommu_probe_device() for each. The inlined check_device() path computes the device's sbdf, calls rlookup_amd_iommu() to find the owning IOMMU, and only afterwards verifies devid <= pci_seg->last_bdf. __rlookup_amd_iommu() indexes rlookup_table[devid] with no bounds check of its own, so for a PCI device whose BDF is not described by the IVRS, the lookup reads past the end of the allocation before the caller's bounds check can run. This was harmless before commit e874c666b15b ("iommu/amd: Change rlookup, irq_lookup, and alias to use kvalloc()"): the table was a zeroed page-order allocation, so the over-read returned NULL and the caller's NULL check skipped the device. After that commit the table is a tight kvcalloc() and the over-read returns adjacent slab contents, which check_device() then dereferences as a struct amd_iommu *, causing a boot-time GPF. Seen on Google Compute Engine ct6e VMs, where the virtualized IVRS describes only the four TPU endpoints 00:04.0-07.0; the gVNIC at 00:08.0 (devid 0x40) indexes 56 bytes past the 456-byte allocation, into the adjacent kmalloc-512 slab object: pci 0000:00:04.0: Adding to iommu group 0 pci 0000:00:05.0: Adding to iommu group 1 pci 0000:00:06.0: Adding to iommu group 2 pci 0000:00:07.0: Adding to iommu group 3 Oops: general protection fault, probably for non-canonical address 0x3a64695f78746382: 0000 [#1] SMP NOPTI CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.18.22 #1 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/06/2025 RIP: 0010:amd_iommu_probe_device+0x54/0x3a0 Call Trace: __iommu_probe_device+0x107/0x520 probe_iommu_group+0x29/0x50 bus_for_each_dev+0x7e/0xe0 iommu_device_register+0xc9/0x240 iommu_go_to_state+0x9c0/0x1c60 amd_iommu_init+0x14/0x40 pci_iommu_init+0x16/0x60 do_one_initcall+0x47/0x2f0 Guard the array access in __rlookup_amd_iommu(). With the fix applied on 6.18.22, the gVNIC at 00:08.0 is skipped cleanly and the VM boots.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected e874c666b15bcb6280c4e747d8de3879bb728829 f0a0f01787ecece814414b0665df879b69849d09 git Not specified
CNA Linux Linux affected e874c666b15bcb6280c4e747d8de3879bb728829 79db4cbab81f07ce69a93d379ebd40d3709ecfb2 git Not specified
CNA Linux Linux affected e874c666b15bcb6280c4e747d8de3879bb728829 07d0f496fe7ec5abe3bee7e38be709521567bb33 git Not specified
CNA Linux Linux affected 6.16 Not specified
CNA Linux Linux unaffected 6.16 semver Not specified
CNA Linux Linux unaffected 6.18.33 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.10 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/79db4cbab81f07ce69a93d379ebd40d3709ecfb2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f0a0f01787ecece814414b0665df879b69849d09 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/07d0f496fe7ec5abe3bee7e38be709521567bb33 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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