userfaultfd: use per-vma locks in userfaultfd operations
All userfaultfd operations, except write-protect, opportunistically use per-vma locks to lock vmas. On failure, attempt again inside mmap_lock critical section. Write-protect operation requires mmap_lock as it iterates over multiple vmas. Link: https://lkml.kernel.org/r/20240215182756.3448972-5-lokeshgidra@google.com Signed-off-by: Lokesh Gidra <lokeshgidra@google.com> Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.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: Jann Horn <jannh@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Mike Rapoport (IBM) <rppt@kernel.org> Cc: Nicolas Geoffray <ngeoffray@google.com> Cc: Peter Xu <peterx@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Tim Murray <timmurray@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lokesh Gidra
Andrew Morton
parent
32af81af2f
commit
867a43a34f
@ -2005,17 +2005,8 @@ static int userfaultfd_move(struct userfaultfd_ctx *ctx,
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return -EINVAL;
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if (mmget_not_zero(mm)) {
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mmap_read_lock(mm);
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/* Re-check after taking map_changing_lock */
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down_read(&ctx->map_changing_lock);
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if (likely(!atomic_read(&ctx->mmap_changing)))
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ret = move_pages(ctx, mm, uffdio_move.dst, uffdio_move.src,
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uffdio_move.len, uffdio_move.mode);
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else
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ret = -EAGAIN;
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up_read(&ctx->map_changing_lock);
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mmap_read_unlock(mm);
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ret = move_pages(ctx, uffdio_move.dst, uffdio_move.src,
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uffdio_move.len, uffdio_move.mode);
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mmput(mm);
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} else {
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return -ESRCH;
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@ -138,9 +138,8 @@ extern long uffd_wp_range(struct vm_area_struct *vma,
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/* move_pages */
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void double_pt_lock(spinlock_t *ptl1, spinlock_t *ptl2);
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void double_pt_unlock(spinlock_t *ptl1, spinlock_t *ptl2);
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ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm,
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unsigned long dst_start, unsigned long src_start,
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unsigned long len, __u64 flags);
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ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
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unsigned long src_start, unsigned long len, __u64 flags);
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int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval,
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struct vm_area_struct *dst_vma,
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struct vm_area_struct *src_vma,
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@ -2158,7 +2158,7 @@ unlock:
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#ifdef CONFIG_USERFAULTFD
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/*
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* The PT lock for src_pmd and the mmap_lock for reading are held by
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* The PT lock for src_pmd and dst_vma/src_vma (for reading) are locked by
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* the caller, but it must return after releasing the page_table_lock.
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* Just move the page from src_pmd to dst_pmd if possible.
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* Return zero if succeeded in moving the page, -EAGAIN if it needs to be
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@ -2181,7 +2181,8 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm
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src_ptl = pmd_lockptr(mm, src_pmd);
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lockdep_assert_held(src_ptl);
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mmap_assert_locked(mm);
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vma_assert_locked(src_vma);
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vma_assert_locked(dst_vma);
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/* Sanity checks before the operation */
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if (WARN_ON_ONCE(!pmd_none(dst_pmdval)) || WARN_ON_ONCE(src_addr & ~HPAGE_PMD_MASK) ||
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384
mm/userfaultfd.c
384
mm/userfaultfd.c
@ -20,19 +20,11 @@
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#include "internal.h"
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static __always_inline
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struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm,
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unsigned long dst_start,
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unsigned long len)
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bool validate_dst_vma(struct vm_area_struct *dst_vma, unsigned long dst_end)
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{
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/*
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* Make sure that the dst range is both valid and fully within a
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* single existing vma.
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*/
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struct vm_area_struct *dst_vma;
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dst_vma = find_vma(dst_mm, dst_start);
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if (!range_in_vma(dst_vma, dst_start, dst_start + len))
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return NULL;
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/* Make sure that the dst range is fully within dst_vma. */
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if (dst_end > dst_vma->vm_end)
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return false;
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/*
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* Check the vma is registered in uffd, this is required to
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@ -40,11 +32,122 @@ struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm,
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* time.
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*/
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if (!dst_vma->vm_userfaultfd_ctx.ctx)
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return NULL;
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return false;
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return true;
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}
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static __always_inline
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struct vm_area_struct *find_vma_and_prepare_anon(struct mm_struct *mm,
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unsigned long addr)
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{
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struct vm_area_struct *vma;
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mmap_assert_locked(mm);
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vma = vma_lookup(mm, addr);
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if (!vma)
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vma = ERR_PTR(-ENOENT);
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else if (!(vma->vm_flags & VM_SHARED) &&
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unlikely(anon_vma_prepare(vma)))
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vma = ERR_PTR(-ENOMEM);
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return vma;
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}
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#ifdef CONFIG_PER_VMA_LOCK
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/*
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* lock_vma() - Lookup and lock vma corresponding to @address.
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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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*
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* Should be called without holding mmap_lock. vma should be unlocked after use
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* with unlock_vma().
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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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* -ENOMEM if anon_vma couldn't be allocated.
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*/
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static struct vm_area_struct *lock_vma(struct mm_struct *mm,
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unsigned long address)
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{
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struct vm_area_struct *vma;
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vma = lock_vma_under_rcu(mm, address);
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if (vma) {
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/*
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* lock_vma_under_rcu() only checks anon_vma for private
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* anonymous mappings. But we need to ensure it is assigned in
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* private file-backed vmas as well.
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*/
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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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else
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return vma;
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}
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mmap_read_lock(mm);
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vma = find_vma_and_prepare_anon(mm, address);
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if (!IS_ERR(vma)) {
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/*
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* We cannot use vma_start_read() as it may fail due to
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* false locked (see comment in vma_start_read()). We
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* can avoid that by directly locking vm_lock under
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* mmap_lock, which guarantees that nobody can lock the
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* vma for write (vma_start_write()) under us.
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*/
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down_read(&vma->vm_lock->lock);
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}
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mmap_read_unlock(mm);
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return vma;
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}
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static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm,
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unsigned long dst_start,
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unsigned long len)
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{
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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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if (IS_ERR(dst_vma) || validate_dst_vma(dst_vma, dst_start + len))
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return dst_vma;
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vma_end_read(dst_vma);
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return ERR_PTR(-ENOENT);
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}
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static void uffd_mfill_unlock(struct vm_area_struct *vma)
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{
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vma_end_read(vma);
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}
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#else
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static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm,
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unsigned long dst_start,
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unsigned long len)
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{
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struct vm_area_struct *dst_vma;
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mmap_read_lock(dst_mm);
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dst_vma = find_vma_and_prepare_anon(dst_mm, dst_start);
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if (IS_ERR(dst_vma))
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goto out_unlock;
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if (validate_dst_vma(dst_vma, dst_start + len))
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return dst_vma;
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dst_vma = ERR_PTR(-ENOENT);
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out_unlock:
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mmap_read_unlock(dst_mm);
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return dst_vma;
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}
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static void uffd_mfill_unlock(struct vm_area_struct *vma)
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{
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mmap_read_unlock(vma->vm_mm);
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}
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#endif
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/* Check if dst_addr is outside of file's size. Must be called with ptl held. */
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static bool mfill_file_over_size(struct vm_area_struct *dst_vma,
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unsigned long dst_addr)
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@ -350,7 +453,8 @@ static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
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#ifdef CONFIG_HUGETLB_PAGE
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/*
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* mfill_atomic processing for HUGETLB vmas. Note that this routine is
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* called with mmap_lock held, it will release mmap_lock before returning.
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* called with either vma-lock or mmap_lock held, it will release the lock
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* before returning.
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*/
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static __always_inline ssize_t mfill_atomic_hugetlb(
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struct userfaultfd_ctx *ctx,
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@ -361,7 +465,6 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
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uffd_flags_t flags)
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{
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struct mm_struct *dst_mm = dst_vma->vm_mm;
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int vm_shared = dst_vma->vm_flags & VM_SHARED;
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ssize_t err;
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pte_t *dst_pte;
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unsigned long src_addr, dst_addr;
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@ -380,7 +483,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
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*/
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if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) {
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up_read(&ctx->map_changing_lock);
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mmap_read_unlock(dst_mm);
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uffd_mfill_unlock(dst_vma);
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return -EINVAL;
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}
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@ -403,24 +506,28 @@ retry:
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* retry, dst_vma will be set to NULL and we must lookup again.
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*/
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if (!dst_vma) {
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dst_vma = uffd_mfill_lock(dst_mm, dst_start, len);
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if (IS_ERR(dst_vma)) {
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err = PTR_ERR(dst_vma);
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goto out;
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}
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err = -ENOENT;
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dst_vma = find_dst_vma(dst_mm, dst_start, len);
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if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
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goto out_unlock;
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if (!is_vm_hugetlb_page(dst_vma))
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goto out_unlock_vma;
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err = -EINVAL;
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if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
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goto out_unlock;
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goto out_unlock_vma;
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vm_shared = dst_vma->vm_flags & VM_SHARED;
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}
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/*
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* If not shared, ensure the dst_vma has a anon_vma.
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*/
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err = -ENOMEM;
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if (!vm_shared) {
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if (unlikely(anon_vma_prepare(dst_vma)))
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/*
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* If memory mappings are changing because of non-cooperative
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* operation (e.g. mremap) running in parallel, bail out and
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* request the user to retry later
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*/
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down_read(&ctx->map_changing_lock);
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err = -EAGAIN;
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if (atomic_read(&ctx->mmap_changing))
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goto out_unlock;
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}
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@ -465,7 +572,7 @@ retry:
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if (unlikely(err == -ENOENT)) {
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up_read(&ctx->map_changing_lock);
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mmap_read_unlock(dst_mm);
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uffd_mfill_unlock(dst_vma);
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BUG_ON(!folio);
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err = copy_folio_from_user(folio,
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@ -474,17 +581,6 @@ retry:
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err = -EFAULT;
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goto out;
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}
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mmap_read_lock(dst_mm);
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down_read(&ctx->map_changing_lock);
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/*
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* If memory mappings are changing because of non-cooperative
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* operation (e.g. mremap) running in parallel, bail out and
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* request the user to retry later
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*/
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if (atomic_read(&ctx->mmap_changing)) {
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err = -EAGAIN;
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break;
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}
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dst_vma = NULL;
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goto retry;
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@ -505,7 +601,8 @@ retry:
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out_unlock:
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up_read(&ctx->map_changing_lock);
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mmap_read_unlock(dst_mm);
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out_unlock_vma:
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uffd_mfill_unlock(dst_vma);
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out:
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if (folio)
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folio_put(folio);
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@ -597,7 +694,15 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx,
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copied = 0;
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folio = NULL;
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retry:
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mmap_read_lock(dst_mm);
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/*
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* Make sure the vma is not shared, that the dst range is
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* both valid and fully within a single existing vma.
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*/
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dst_vma = uffd_mfill_lock(dst_mm, dst_start, len);
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if (IS_ERR(dst_vma)) {
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err = PTR_ERR(dst_vma);
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goto out;
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}
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/*
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* If memory mappings are changing because of non-cooperative
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@ -609,15 +714,6 @@ retry:
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if (atomic_read(&ctx->mmap_changing))
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goto out_unlock;
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/*
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* Make sure the vma is not shared, that the dst range is
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* both valid and fully within a single existing vma.
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*/
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err = -ENOENT;
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dst_vma = find_dst_vma(dst_mm, dst_start, len);
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if (!dst_vma)
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goto out_unlock;
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err = -EINVAL;
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/*
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* shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
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@ -647,16 +743,6 @@ retry:
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uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE))
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goto out_unlock;
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/*
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* Ensure the dst_vma has a anon_vma or this page
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* would get a NULL anon_vma when moved in the
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* dst_vma.
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*/
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err = -ENOMEM;
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if (!(dst_vma->vm_flags & VM_SHARED) &&
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unlikely(anon_vma_prepare(dst_vma)))
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goto out_unlock;
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while (src_addr < src_start + len) {
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pmd_t dst_pmdval;
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@ -699,7 +785,7 @@ retry:
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void *kaddr;
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up_read(&ctx->map_changing_lock);
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mmap_read_unlock(dst_mm);
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uffd_mfill_unlock(dst_vma);
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BUG_ON(!folio);
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kaddr = kmap_local_folio(folio, 0);
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@ -730,7 +816,7 @@ retry:
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out_unlock:
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up_read(&ctx->map_changing_lock);
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mmap_read_unlock(dst_mm);
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uffd_mfill_unlock(dst_vma);
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out:
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if (folio)
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folio_put(folio);
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@ -1267,27 +1353,136 @@ static int validate_move_areas(struct userfaultfd_ctx *ctx,
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if (!vma_is_anonymous(src_vma) || !vma_is_anonymous(dst_vma))
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return -EINVAL;
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/*
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* Ensure the dst_vma has a anon_vma or this page
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* would get a NULL anon_vma when moved in the
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* dst_vma.
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*/
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if (unlikely(anon_vma_prepare(dst_vma)))
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return -ENOMEM;
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return 0;
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}
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static __always_inline
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int find_vmas_mm_locked(struct mm_struct *mm,
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unsigned long dst_start,
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unsigned long src_start,
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struct vm_area_struct **dst_vmap,
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struct vm_area_struct **src_vmap)
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{
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struct vm_area_struct *vma;
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mmap_assert_locked(mm);
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vma = find_vma_and_prepare_anon(mm, dst_start);
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if (IS_ERR(vma))
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return PTR_ERR(vma);
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*dst_vmap = vma;
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/* Skip finding src_vma if src_start is in dst_vma */
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if (src_start >= vma->vm_start && src_start < vma->vm_end)
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goto out_success;
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vma = vma_lookup(mm, src_start);
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if (!vma)
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return -ENOENT;
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out_success:
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*src_vmap = vma;
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return 0;
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}
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#ifdef CONFIG_PER_VMA_LOCK
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static int uffd_move_lock(struct mm_struct *mm,
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unsigned long dst_start,
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unsigned long src_start,
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struct vm_area_struct **dst_vmap,
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struct vm_area_struct **src_vmap)
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{
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struct vm_area_struct *vma;
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int err;
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vma = lock_vma(mm, dst_start);
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if (IS_ERR(vma))
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return PTR_ERR(vma);
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*dst_vmap = vma;
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||||
/*
|
||||
* Skip finding src_vma if src_start is in dst_vma. This also ensures
|
||||
* that we don't lock the same vma twice.
|
||||
*/
|
||||
if (src_start >= vma->vm_start && src_start < vma->vm_end) {
|
||||
*src_vmap = vma;
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Using lock_vma() to get src_vma can lead to following deadlock:
|
||||
*
|
||||
* Thread1 Thread2
|
||||
* ------- -------
|
||||
* vma_start_read(dst_vma)
|
||||
* mmap_write_lock(mm)
|
||||
* vma_start_write(src_vma)
|
||||
* vma_start_read(src_vma)
|
||||
* mmap_read_lock(mm)
|
||||
* vma_start_write(dst_vma)
|
||||
*/
|
||||
*src_vmap = lock_vma_under_rcu(mm, src_start);
|
||||
if (likely(*src_vmap))
|
||||
return 0;
|
||||
|
||||
/* Undo any locking and retry in mmap_lock critical section */
|
||||
vma_end_read(*dst_vmap);
|
||||
|
||||
mmap_read_lock(mm);
|
||||
err = find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap);
|
||||
if (!err) {
|
||||
/*
|
||||
* See comment in lock_vma() as to why not using
|
||||
* vma_start_read() here.
|
||||
*/
|
||||
down_read(&(*dst_vmap)->vm_lock->lock);
|
||||
if (*dst_vmap != *src_vmap)
|
||||
down_read(&(*src_vmap)->vm_lock->lock);
|
||||
}
|
||||
mmap_read_unlock(mm);
|
||||
return err;
|
||||
}
|
||||
|
||||
static void uffd_move_unlock(struct vm_area_struct *dst_vma,
|
||||
struct vm_area_struct *src_vma)
|
||||
{
|
||||
vma_end_read(src_vma);
|
||||
if (src_vma != dst_vma)
|
||||
vma_end_read(dst_vma);
|
||||
}
|
||||
|
||||
#else
|
||||
|
||||
static int uffd_move_lock(struct mm_struct *mm,
|
||||
unsigned long dst_start,
|
||||
unsigned long src_start,
|
||||
struct vm_area_struct **dst_vmap,
|
||||
struct vm_area_struct **src_vmap)
|
||||
{
|
||||
int err;
|
||||
|
||||
mmap_read_lock(mm);
|
||||
err = find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap);
|
||||
if (err)
|
||||
mmap_read_unlock(mm);
|
||||
return err;
|
||||
}
|
||||
|
||||
static void uffd_move_unlock(struct vm_area_struct *dst_vma,
|
||||
struct vm_area_struct *src_vma)
|
||||
{
|
||||
mmap_assert_locked(src_vma->vm_mm);
|
||||
mmap_read_unlock(dst_vma->vm_mm);
|
||||
}
|
||||
#endif
|
||||
|
||||
/**
|
||||
* move_pages - move arbitrary anonymous pages of an existing vma
|
||||
* @ctx: pointer to the userfaultfd context
|
||||
* @mm: the address space to move pages
|
||||
* @dst_start: start of the destination virtual memory range
|
||||
* @src_start: start of the source virtual memory range
|
||||
* @len: length of the virtual memory range
|
||||
* @mode: flags from uffdio_move.mode
|
||||
*
|
||||
* Must be called with mmap_lock held for read.
|
||||
* It will either use the mmap_lock in read mode or per-vma locks
|
||||
*
|
||||
* move_pages() remaps arbitrary anonymous pages atomically in zero
|
||||
* copy. It only works on non shared anonymous pages because those can
|
||||
@ -1355,10 +1550,10 @@ static int validate_move_areas(struct userfaultfd_ctx *ctx,
|
||||
* could be obtained. This is the only additional complexity added to
|
||||
* the rmap code to provide this anonymous page remapping functionality.
|
||||
*/
|
||||
ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm,
|
||||
unsigned long dst_start, unsigned long src_start,
|
||||
unsigned long len, __u64 mode)
|
||||
ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
|
||||
unsigned long src_start, unsigned long len, __u64 mode)
|
||||
{
|
||||
struct mm_struct *mm = ctx->mm;
|
||||
struct vm_area_struct *src_vma, *dst_vma;
|
||||
unsigned long src_addr, dst_addr;
|
||||
pmd_t *src_pmd, *dst_pmd;
|
||||
@ -1376,28 +1571,34 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm,
|
||||
WARN_ON_ONCE(dst_start + len <= dst_start))
|
||||
goto out;
|
||||
|
||||
err = uffd_move_lock(mm, dst_start, src_start, &dst_vma, &src_vma);
|
||||
if (err)
|
||||
goto out;
|
||||
|
||||
/* Re-check after taking map_changing_lock */
|
||||
err = -EAGAIN;
|
||||
down_read(&ctx->map_changing_lock);
|
||||
if (likely(atomic_read(&ctx->mmap_changing)))
|
||||
goto out_unlock;
|
||||
/*
|
||||
* Make sure the vma is not shared, that the src and dst remap
|
||||
* ranges are both valid and fully within a single existing
|
||||
* vma.
|
||||
*/
|
||||
src_vma = find_vma(mm, src_start);
|
||||
if (!src_vma || (src_vma->vm_flags & VM_SHARED))
|
||||
goto out;
|
||||
if (src_start < src_vma->vm_start ||
|
||||
src_start + len > src_vma->vm_end)
|
||||
goto out;
|
||||
err = -EINVAL;
|
||||
if (src_vma->vm_flags & VM_SHARED)
|
||||
goto out_unlock;
|
||||
if (src_start + len > src_vma->vm_end)
|
||||
goto out_unlock;
|
||||
|
||||
dst_vma = find_vma(mm, dst_start);
|
||||
if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))
|
||||
goto out;
|
||||
if (dst_start < dst_vma->vm_start ||
|
||||
dst_start + len > dst_vma->vm_end)
|
||||
goto out;
|
||||
if (dst_vma->vm_flags & VM_SHARED)
|
||||
goto out_unlock;
|
||||
if (dst_start + len > dst_vma->vm_end)
|
||||
goto out_unlock;
|
||||
|
||||
err = validate_move_areas(ctx, src_vma, dst_vma);
|
||||
if (err)
|
||||
goto out;
|
||||
goto out_unlock;
|
||||
|
||||
for (src_addr = src_start, dst_addr = dst_start;
|
||||
src_addr < src_start + len;) {
|
||||
@ -1514,6 +1715,9 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm,
|
||||
moved += step_size;
|
||||
}
|
||||
|
||||
out_unlock:
|
||||
up_read(&ctx->map_changing_lock);
|
||||
uffd_move_unlock(dst_vma, src_vma);
|
||||
out:
|
||||
VM_WARN_ON(moved < 0);
|
||||
VM_WARN_ON(err > 0);
|
||||
|
||||
Loading…
Reference in New Issue
Block a user