Commit 6c64f2bb authored Aug 23, 2019 by Ralph Campbell Committed by Jason Gunthorpe Aug 27, 2019

mm/hmm: hmm_range_fault() NULL pointer bug

Although hmm_range_fault() calls find_vma() to make sure that a vma exists
before calling walk_page_range(), hmm_vma_walk_hole() can still be called
with walk->vma == NULL if the start and end address are not contained
within the vma range.

 hmm_range_fault() /* calls find_vma() but no range check */
  walk_page_range() /* calls find_vma(), sets walk->vma = NULL */
   __walk_page_range()
    walk_pgd_range()
     walk_p4d_range()
      walk_pud_range()
       hmm_vma_walk_hole()
        hmm_vma_walk_hole_()
         hmm_vma_do_fault()
          handle_mm_fault(vma=0)

Link: https://lore.kernel.org/r/20190823221753.2514-2-rcampbell@nvidia.com


Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

parent e3fe8e55

mm/hmm.c

+9 −4

Original line number	Diff line number	Diff line
		@@ -229,6 +229,9 @@ static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
		struct vm_area_struct *vma = walk->vma;
		vm_fault_t ret;

		if (!vma)
		goto err;

		if (hmm_vma_walk->flags & HMM_FAULT_ALLOW_RETRY)
		flags \|= FAULT_FLAG_ALLOW_RETRY;
		if (write_fault)
		@@ -239,12 +242,14 @@ static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
		/* Note, handle_mm_fault did up_read(&mm->mmap_sem)) */
		return -EAGAIN;
		}
		if (ret & VM_FAULT_ERROR) {
		*pfn = range->values[HMM_PFN_ERROR];
		return -EFAULT;
		}
		if (ret & VM_FAULT_ERROR)
		goto err;

		return -EBUSY;

		err:
		*pfn = range->values[HMM_PFN_ERROR];
		return -EFAULT;
		}

		static int hmm_pfns_bad(unsigned long addr,