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commit 5cbf3264bc715e9eb384e2b68601f8c02bb9a61d upstream. 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: 73fa0d10d077 ("vfio: Type1 IOMMU implementation") Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.