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mm: fix some minor per-VMA lock issues in userfaultfd
Rename lock_vma() to uffd_lock_vma() because it really is uffd specific. Remove comment referencing unlock_vma() which doesn't exist. Fix the comment about lock_vma_under_rcu() which I just made incorrect. Link: https://lkml.kernel.org/r/20240426144506.1290619-4-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Suren Baghdasaryan <surenb@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@ -56,17 +56,16 @@ struct vm_area_struct *find_vma_and_prepare_anon(struct mm_struct *mm,
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#ifdef CONFIG_PER_VMA_LOCK
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#ifdef CONFIG_PER_VMA_LOCK
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/*
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/*
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* lock_vma() - Lookup and lock vma corresponding to @address.
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* uffd_lock_vma() - Lookup and lock vma corresponding to @address.
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* @mm: mm to search vma in.
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* @mm: mm to search vma in.
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* @address: address that the vma should contain.
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* @address: address that the vma should contain.
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*
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*
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* Should be called without holding mmap_lock. vma should be unlocked after use
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* Should be called without holding mmap_lock.
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* with unlock_vma().
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*
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*
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* Return: A locked vma containing @address, -ENOENT if no vma is found, or
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* Return: A locked vma containing @address, -ENOENT if no vma is found, or
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* -ENOMEM if anon_vma couldn't be allocated.
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* -ENOMEM if anon_vma couldn't be allocated.
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*/
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*/
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static struct vm_area_struct *lock_vma(struct mm_struct *mm,
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static struct vm_area_struct *uffd_lock_vma(struct mm_struct *mm,
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unsigned long address)
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unsigned long address)
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{
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{
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struct vm_area_struct *vma;
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struct vm_area_struct *vma;
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@ -74,9 +73,8 @@ static struct vm_area_struct *lock_vma(struct mm_struct *mm,
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vma = lock_vma_under_rcu(mm, address);
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vma = lock_vma_under_rcu(mm, address);
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if (vma) {
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if (vma) {
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/*
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/*
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* lock_vma_under_rcu() only checks anon_vma for private
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* We know we're going to need to use anon_vma, so check
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* anonymous mappings. But we need to ensure it is assigned in
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* that early.
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* private file-backed vmas as well.
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*/
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*/
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if (!(vma->vm_flags & VM_SHARED) && unlikely(!vma->anon_vma))
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if (!(vma->vm_flags & VM_SHARED) && unlikely(!vma->anon_vma))
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vma_end_read(vma);
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vma_end_read(vma);
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@ -107,7 +105,7 @@ static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm,
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{
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{
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struct vm_area_struct *dst_vma;
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struct vm_area_struct *dst_vma;
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dst_vma = lock_vma(dst_mm, dst_start);
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dst_vma = uffd_lock_vma(dst_mm, dst_start);
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if (IS_ERR(dst_vma) || validate_dst_vma(dst_vma, dst_start + len))
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if (IS_ERR(dst_vma) || validate_dst_vma(dst_vma, dst_start + len))
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return dst_vma;
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return dst_vma;
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@ -1401,7 +1399,7 @@ static int uffd_move_lock(struct mm_struct *mm,
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struct vm_area_struct *vma;
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struct vm_area_struct *vma;
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int err;
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int err;
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vma = lock_vma(mm, dst_start);
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vma = uffd_lock_vma(mm, dst_start);
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if (IS_ERR(vma))
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if (IS_ERR(vma))
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return PTR_ERR(vma);
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return PTR_ERR(vma);
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@ -1416,7 +1414,7 @@ static int uffd_move_lock(struct mm_struct *mm,
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}
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}
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/*
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/*
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* Using lock_vma() to get src_vma can lead to following deadlock:
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* Using uffd_lock_vma() to get src_vma can lead to following deadlock:
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*
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*
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* Thread1 Thread2
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* Thread1 Thread2
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* ------- -------
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* ------- -------
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@ -1438,7 +1436,7 @@ static int uffd_move_lock(struct mm_struct *mm,
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err = find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap);
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err = find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap);
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if (!err) {
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if (!err) {
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/*
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/*
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* See comment in lock_vma() as to why not using
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* See comment in uffd_lock_vma() as to why not using
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* vma_start_read() here.
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* vma_start_read() here.
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*/
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*/
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down_read(&(*dst_vmap)->vm_lock->lock);
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down_read(&(*dst_vmap)->vm_lock->lock);
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