On Wed, Feb 28, 2024 at 09:55:24AM +0800, mawupeng wrote: > On 2024/2/27 21:15, David Hildenbrand wrote: > > On 27.02.24 14:00, David Hildenbrand wrote: > >> On 27.02.24 13:28, Wupeng Ma wrote: > >>> We find that a warn will be produced during our test, the detail log is > >>> shown in the end. > >>> > >>> The core problem of this warn is that the first pfn of this pfnmap vma is > >>> cleared during memory-failure. Digging into the source we find that this > >>> problem can be triggered as following: > >>> > >>> // mmap with MAP_PRIVATE and specific fd which hook mmap > >>> mmap(MAP_PRIVATE, fd) > >>> __mmap_region > >>> remap_pfn_range > >>> // set vma with pfnmap and the prot of pte is read only > >>> > >> > >> Okay, so we get a MAP_PRIVATE VM_PFNMAP I assume. > >> > >> What fd is that exactly? Often, we disallow private mappings in the > >> mmap() callback (for a good reason). > > just a device fd with device-specify mmap which use remap_pfn_range to assign memory. But what meaning do you want MAP_PRIVATE of this fd to have? Does it make sense to permit this, or should you rather just return -EINVAL if somebody tries to mmap() with MAP_PRIVATE set?
