> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Friday, November 29, 2024 10:05 AM
>
> The current implementation removes cache tags after disabling ATS,
> leading to potential memory leaks and kernel crashes. Specifically,
> CACHE_TAG_DEVTLB type cache tags may still remain in the list even
> after the domain is freed, causing a use-after-free condition.
>
> This issue really shows up when multiple VFs from different PFs
> passed through to a single user-space process via vfio-pci. In such
> cases, the kernel may crash with kernel messages like:
Is "multiple VFs from different PFs" the key to trigger the problem?
what about multiple VFs from the same PF or just assigning multiple
devices to a single process/vm?
My understanding from the below fix is that this issue will be triggered
as long as the domain is still being actively used after one device with
ATS is detached from it, i.e. sounds like a problem in multi-device
assignment scenario.
>
> BUG: kernel NULL pointer dereference, address: 0000000000000014
> PGD 19036a067 P4D 1940a3067 PUD 136c9b067 PMD 0
> Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 74 UID: 0 PID: 3183 Comm: testCli Not tainted 6.11.9 #2
> RIP: 0010:cache_tag_flush_range+0x9b/0x250
> Call Trace:
> <TASK>
> ? __die+0x1f/0x60
> ? page_fault_oops+0x163/0x590
> ? exc_page_fault+0x72/0x190
> ? asm_exc_page_fault+0x22/0x30
> ? cache_tag_flush_range+0x9b/0x250
> ? cache_tag_flush_range+0x5d/0x250
> intel_iommu_tlb_sync+0x29/0x40
> intel_iommu_unmap_pages+0xfe/0x160
> __iommu_unmap+0xd8/0x1a0
> vfio_unmap_unpin+0x182/0x340 [vfio_iommu_type1]
> vfio_remove_dma+0x2a/0xb0 [vfio_iommu_type1]
> vfio_iommu_type1_ioctl+0xafa/0x18e0 [vfio_iommu_type1]
>
> Move cache_tag_unassign_domain() before iommu_disable_pci_caps() to fix
> it.
>
> Fixes: 3b1d9e2b2d68 ("iommu/vt-d: Add cache tag assignment interface")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
