Use follow_pfn() to get the PFN of a PFNMAP VMA instead of assuming that
vma->vm_pgoff holds the base PFN of the VMA. This fixes a bug where
attempting to do VFIO_IOMMU_MAP_DMA on an arbitrary PFNMAP'd region of
memory calculates garbage for the PFN.
Hilariously, this only got detected because the first "PFN" calculated
by vaddr_get_pfn() is PFN 0 (vma->vm_pgoff==0), and iommu_iova_to_phys()
uses PA==0 as an error, which triggers a WARN in vfio_unmap_unpin()
because the translation "failed". PFN 0 is now unconditionally reserved
on x86 in order to mitigate L1TF, which causes is_invalid_reserved_pfn()
to return true and in turns results in vaddr_get_pfn() returning success
for PFN 0. Eventually the bogus calculation runs into PFNs that aren't
reserved and leads to failure in vfio_pin_map_dma(). The subsequent
call to vfio_remove_dma() attempts to unmap PFN 0 and WARNs.
WARNING: CPU: 8 PID: 5130 at drivers/vfio/vfio_iommu_type1.c:750 vfio_unmap_unpin+0x2e1/0x310 [vfio_iommu_type1]
Modules linked in: vfio_pci vfio_virqfd vfio_iommu_type1 vfio ...
CPU: 8 PID: 5130 Comm: sgx Tainted: G W 5.6.0-rc5-705d787c7fee-vfio+ #3
Hardware name: Intel Corporation Mehlow UP Server Platform/Moss Beach Server, BIOS CNLSE2R1.D00.X119.B49.1803010910 03/01/2018
RIP: 0010:vfio_unmap_unpin+0x2e1/0x310 [vfio_iommu_type1]
Code: <0f> 0b 49 81 c5 00 10 00 00 e9 c5 fe ff ff bb 00 10 00 00 e9 3d fe
RSP: 0018:ffffbeb5039ebda8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff9a55cbf8d480 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff9a52b771c200
RBP: 0000000000000000 R08: 0000000000000040 R09: 00000000fffffff2
R10: 0000000000000001 R11: ffff9a51fa896000 R12: 0000000184010000
R13: 0000000184000000 R14: 0000000000010000 R15: ffff9a55cb66ea08
FS: 00007f15d3830b40(0000) GS:ffff9a55d5600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000561cf39429e0 CR3: 000000084f75f005 CR4: 00000000003626e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
vfio_remove_dma+0x17/0x70 [vfio_iommu_type1]
vfio_iommu_type1_ioctl+0x9e3/0xa7b [vfio_iommu_type1]
ksys_ioctl+0x92/0xb0
__x64_sys_ioctl+0x16/0x20
do_syscall_64+0x4c/0x180
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f15d04c75d7
Code: <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 81 48 2d 00 f7 d8 64 89 01 48
Fixes: 73fa0d10d0 ("vfio: Type1 IOMMU implementation")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
5cbf3264bc