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author | Filippo Sironi <sironi@amazon.de> | 2019-01-31 21:24:33 +0100 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2019-04-30 21:32:45 +0200 |
commit | bd53cb35a3e9adb73a834a36586e9ad80e877767 (patch) | |
tree | 851b21fe7617e39fa130ac9944da1c3a64378d90 /arch/x86/kvm | |
parent | 3d5f6beb74a00bcc308612ee007e3e0c6126c397 (diff) | |
download | linux-stable-bd53cb35a3e9adb73a834a36586e9ad80e877767.tar.gz linux-stable-bd53cb35a3e9adb73a834a36586e9ad80e877767.tar.bz2 linux-stable-bd53cb35a3e9adb73a834a36586e9ad80e877767.zip |
X86/KVM: Handle PFNs outside of kernel reach when touching GPTEs
cmpxchg_gpte() calls get_user_pages_fast() to retrieve the number of
pages and the respective struct page to map in the kernel virtual
address space.
This doesn't work if get_user_pages_fast() is invoked with a userspace
virtual address that's backed by PFNs outside of kernel reach (e.g., when
limiting the kernel memory with mem= in the command line and using
/dev/mem to map memory).
If get_user_pages_fast() fails, look up the VMA that back the userspace
virtual address, compute the PFN and the physical address, and map it in
the kernel virtual address space with memremap().
Signed-off-by: Filippo Sironi <sironi@amazon.de>
Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm')
-rw-r--r-- | arch/x86/kvm/paging_tmpl.h | 38 |
1 files changed, 29 insertions, 9 deletions
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 6bdca39829bc..c40af67d0f44 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -141,15 +141,35 @@ static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, struct page *page; npages = get_user_pages_fast((unsigned long)ptep_user, 1, 1, &page); - /* Check if the user is doing something meaningless. */ - if (unlikely(npages != 1)) - return -EFAULT; - - table = kmap_atomic(page); - ret = CMPXCHG(&table[index], orig_pte, new_pte); - kunmap_atomic(table); - - kvm_release_page_dirty(page); + if (likely(npages == 1)) { + table = kmap_atomic(page); + ret = CMPXCHG(&table[index], orig_pte, new_pte); + kunmap_atomic(table); + + kvm_release_page_dirty(page); + } else { + struct vm_area_struct *vma; + unsigned long vaddr = (unsigned long)ptep_user & PAGE_MASK; + unsigned long pfn; + unsigned long paddr; + + down_read(¤t->mm->mmap_sem); + vma = find_vma_intersection(current->mm, vaddr, vaddr + PAGE_SIZE); + if (!vma || !(vma->vm_flags & VM_PFNMAP)) { + up_read(¤t->mm->mmap_sem); + return -EFAULT; + } + pfn = ((vaddr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; + paddr = pfn << PAGE_SHIFT; + table = memremap(paddr, PAGE_SIZE, MEMREMAP_WB); + if (!table) { + up_read(¤t->mm->mmap_sem); + return -EFAULT; + } + ret = CMPXCHG(&table[index], orig_pte, new_pte); + memunmap(table); + up_read(¤t->mm->mmap_sem); + } return (ret != orig_pte); } |