From c18ce674d548c00faa6b7e760bacbaf1f39315f3 Mon Sep 17 00:00:00 2001 From: Ralph Campbell Date: Fri, 23 Aug 2019 15:17:53 -0700 Subject: mm/hmm: hmm_range_fault() infinite loop Normally, callers to handle_mm_fault() are supposed to check the vma->vm_flags first. hmm_range_fault() checks for VM_READ but doesn't check for VM_WRITE if the caller requests a page to be faulted in with write permission (via the hmm_range.pfns[] value). If the vma is write protected, this can result in an infinite loop: hmm_range_fault() walk_page_range() ... hmm_vma_walk_hole() hmm_vma_walk_hole_() hmm_vma_do_fault() handle_mm_fault(FAULT_FLAG_WRITE) /* returns VM_FAULT_WRITE */ /* returns -EBUSY */ /* returns -EBUSY */ /* returns -EBUSY */ /* loops on -EBUSY and range->valid */ Prevent this by checking for vma->vm_flags & VM_WRITE before calling handle_mm_fault(). Link: https://lore.kernel.org/r/20190823221753.2514-3-rcampbell@nvidia.com Signed-off-by: Ralph Campbell Reviewed-by: Christoph Hellwig Reviewed-by: Jason Gunthorpe Signed-off-by: Jason Gunthorpe --- mm/hmm.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'mm/hmm.c') diff --git a/mm/hmm.c b/mm/hmm.c index 29371485fe94..4882b83aeccb 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -292,6 +292,9 @@ static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end, hmm_vma_walk->last = addr; i = (addr - range->start) >> PAGE_SHIFT; + if (write_fault && walk->vma && !(walk->vma->vm_flags & VM_WRITE)) + return -EPERM; + for (; addr < end; addr += PAGE_SIZE, i++) { pfns[i] = range->values[HMM_PFN_NONE]; if (fault || write_fault) { -- cgit v1.2.3