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UPSTREAM: userfaultfd: fix deadlock warning when locking src and dst VMAs

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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>

(cherry picked from commit 30af24facf0aed12dec23bdf6eac6a907f88306a)

Bug: 320478828
Change-Id: I56d7e33878d6248bba28e1e4204e2b9005d87e4d
Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
This commit is contained in:
Lokesh Gidra
2024-03-21 16:58:18 -07:00
parent ce2896c0c6
commit 8dd482be44
1 changed files with 2 additions and 1 deletions
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3
mm/userfaultfd.c
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@@ -1383,7 +1383,8 @@ static int uffd_move_lock(struct mm_struct *mm,
*/
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;