From: David Hildenbrand david@redhat.com
commit a8b92b8c1eac8d655a97b1e90f4d83c25d9b9a18 upstream.
We should not walk/touch page tables outside of VMA boundaries when holding only the mmap sem in read mode. Evil user space can modify the VMA layout just before this function runs and e.g., trigger races with page table removal code since commit dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap").
find_vma() does not check if the address is >= the VMA start address; use vma_lookup() instead.
Reviewed-by: Niklas Schnelle schnelle@linux.ibm.com Reviewed-by: Liam R. Howlett Liam.Howlett@oracle.com Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap") Signed-off-by: David Hildenbrand david@redhat.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/s390/pci/pci_mmio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/s390/pci/pci_mmio.c +++ b/arch/s390/pci/pci_mmio.c @@ -128,7 +128,7 @@ static long get_pfn(unsigned long user_a down_read(¤t->mm->mmap_sem); ret = -EINVAL; vma = find_vma(current->mm, user_addr); - if (!vma) + if (!vma || user_addr < vma->vm_start) goto out; ret = -EACCES; if (!(vma->vm_flags & access))