| From: Lokesh Gidra <lokeshgidra@google.com> |
| Subject: userfaultfd: fix deadlock warning when locking src and dst VMAs |
| Date: Thu, 21 Mar 2024 16:58:18 -0700 |
| |
| Use down_read_nested() to avoid the warning. |
| |
| Link: https://lkml.kernel.org/r/20240321235818.125118-1-lokeshgidra@google.com |
| Fixes: 867a43a34ff8 ("userfaultfd: use per-vma locks in userfaultfd operations") |
| Reported-by: syzbot+49056626fe41e01f2ba7@syzkaller.appspotmail.com |
| Signed-off-by: Lokesh Gidra <lokeshgidra@google.com> |
| Cc: Andrea Arcangeli <aarcange@redhat.com> |
| Cc: Axel Rasmussen <axelrasmussen@google.com> |
| Cc: Brian Geffon <bgeffon@google.com> |
| Cc: David Hildenbrand <david@redhat.com> |
| Cc: Hillf Danton <hdanton@sina.com> |
| Cc: Jann Horn <jannh@google.com> [Bug #2] |
| Cc: Kalesh Singh <kaleshsingh@google.com> |
| Cc: Lokesh Gidra <lokeshgidra@google.com> |
| Cc: Mike Rapoport (IBM) <rppt@kernel.org> |
| Cc: Nicolas Geoffray <ngeoffray@google.com> |
| Cc: Peter Xu <peterx@redhat.com> |
| Cc: Suren Baghdasaryan <surenb@google.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| mm/userfaultfd.c | 3 ++- |
| 1 file changed, 2 insertions(+), 1 deletion(-) |
| |
| --- a/mm/userfaultfd.c~userfaultfd-fix-deadlock-warning-when-locking-src-and-dst-vmas |
| +++ a/mm/userfaultfd.c |
| @@ -1444,7 +1444,8 @@ static int uffd_move_lock(struct mm_stru |
| */ |
| down_read(&(*dst_vmap)->vm_lock->lock); |
| if (*dst_vmap != *src_vmap) |
| - down_read(&(*src_vmap)->vm_lock->lock); |
| + down_read_nested(&(*src_vmap)->vm_lock->lock, |
| + SINGLE_DEPTH_NESTING); |
| } |
| mmap_read_unlock(mm); |
| return err; |
| _ |
