On Fri, Aug 23, 2019 at 03:17:53PM -0700, Ralph Campbell wrote: > 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(). > > Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx> Looks good, Reviewed-by: Christoph Hellwig <hch@xxxxxx>
