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mm/mmap: prevent pagefault handler from racing with mmu_notifier registration 

Page fault handlers might need to fire MMU notifications while a new
notifier is being registered.  Modify mm_take_all_locks to write-lock all
VMAs and prevent this race with page fault handlers that would hold VMA
locks.  VMAs are locked before i_mmap_rwsem and anon_vma to keep the same
locking order as in page fault handlers.

Link: https://lkml.kernel.org/r/20230227173632.3292573-22-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Suren Baghdasaryan 2023-02-27 09:36:20 -08:00 committed by Andrew Morton
parent f2e13784c1
commit eeff9a5d47
1 changed files with 9 additions and 0 deletions
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9
mm/mmap.c
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@ -3494,6 +3494,7 @@ static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
* of mm/rmap.c:
* - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for
* hugetlb mapping);
* - all vmas marked locked
* - all i_mmap_rwsem locks;
* - all anon_vma->rwseml
*
@ -3516,6 +3517,13 @@ int mm_take_all_locks(struct mm_struct *mm)
mutex_lock(&mm_all_locks_mutex);
mas_for_each(&mas, vma, ULONG_MAX) {
if (signal_pending(current))
goto out_unlock;
vma_start_write(vma);
}
mas_set(&mas, 0);
mas_for_each(&mas, vma, ULONG_MAX) {
if (signal_pending(current))
goto out_unlock;
@ -3605,6 +3613,7 @@ void mm_drop_all_locks(struct mm_struct *mm)
if (vma->vm_file && vma->vm_file->f_mapping)
vm_unlock_mapping(vma->vm_file->f_mapping);
}
vma_end_write_all(mm);
mutex_unlock(&mm_all_locks_mutex);
}