From 6bfdc3056ca81323870e7c2bee3a62aa9faa78d9 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Thu, 9 Sep 2021 16:59:42 +0200 Subject: [PATCH] s390/pci_mmio: fully validate the VMA before calling follow_pte() 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 Reviewed-by: Liam R. Howlett Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap") Signed-off-by: David Hildenbrand Signed-off-by: Vasily Gorbik Signed-off-by: Greg Kroah-Hartman --- arch/s390/pci/pci_mmio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/s390/pci/pci_mmio.c b/arch/s390/pci/pci_mmio.c index 020a2c514d96..921f0fc12f1f 100644 --- 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_addr, unsigned long access, 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))