Commit 444eeb17 authored by Suren Baghdasaryan's avatar Suren Baghdasaryan Committed by Andrew Morton
Browse files

mm: prevent userfaults to be handled under per-vma lock 

Due to the possibility of handle_userfault dropping mmap_lock, avoid fault
handling under VMA lock and retry holding mmap_lock.  This can be handled
more gracefully in the future.

Link: https://lkml.kernel.org/r/20230227173632.3292573-28-surenb@google.com


Signed-off-by: default avatarSuren Baghdasaryan <surenb@google.com>
Suggested-by: default avatarPeter Xu <peterx@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 17c05f18

mm/memory.c

+9 −0
Original line number Diff line number Diff line
@@ -5266,6 +5266,15 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, 
	if (!vma_start_read(vma))

		goto inval;



	/*

	 * Due to the possibility of userfault handler dropping mmap_lock, avoid

	 * it for now and fall back to page fault handling under mmap_lock.

	 */

	if (userfaultfd_armed(vma)) {

		vma_end_read(vma);

		goto inval;

	}



	/* Check since vm_start/vm_end might change before we lock the VMA */

	if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {

		vma_end_read(vma);