diff options
| -rw-r--r-- | include/linux/mm.h | 6 | ||||
| -rw-r--r-- | mm/memory.c | 6 |
2 files changed, 10 insertions, 2 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 6f959d8ca4b4..f0d5be9dc736 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -608,7 +608,11 @@ enum { /* * Flags which should result in page tables being copied on fork. These are * flags which indicate that the VMA maps page tables which cannot be - * reconsistuted upon page fault, so necessitate page table copying upon + * reconsistuted upon page fault, so necessitate page table copying upon fork. + * + * Note that these flags should be compared with the DESTINATION VMA not the + * source, as VM_UFFD_WP may not be propagated to destination, while all other + * flags will be. * * VM_PFNMAP / VM_MIXEDMAP - These contain kernel-mapped data which cannot be * reasonably reconstructed on page fault. diff --git a/mm/memory.c b/mm/memory.c index a0822b564cc0..da360a6eb8a4 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1465,7 +1465,11 @@ copy_p4d_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, static bool vma_needs_copy(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) { - if (src_vma->vm_flags & VM_COPY_ON_FORK) + /* + * We check against dst_vma as while sane VMA flags will have been + * copied, VM_UFFD_WP may be set only on dst_vma. + */ + if (dst_vma->vm_flags & VM_COPY_ON_FORK) return true; /* * The presence of an anon_vma indicates an anonymous VMA has page |