mm/migrate_device.c: flush TLB while holding PTL

stable inclusion
from stable-v5.10.147
commit 1002d5fef406c8dc685679aedb16938ad57d968c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6D0W8

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1002d5fef406c8dc685679aedb16938ad57d968c

--------------------------------

commit 60bae737 upstream.

When clearing a PTE the TLB should be flushed whilst still holding the PTL
to avoid a potential race with madvise/munmap/etc.  For example consider
the following sequence:

  CPU0                          CPU1
  ----                          ----

  migrate_vma_collect_pmd()
  pte_unmap_unlock()
                                madvise(MADV_DONTNEED)
                                -> zap_pte_range()
                                pte_offset_map_lock()
                                [ PTE not present, TLB not flushed ]
                                pte_unmap_unlock()
                                [ page is still accessible via stale TLB ]
  flush_tlb_range()

In this case the page may still be accessed via the stale TLB entry after
madvise returns.  Fix this by flushing the TLB while holding the PTL.

Fixes: 8c3328f1 ("mm/migrate: migrate_vma() unmap page from vma while collecting pages")
Link: https://lkml.kernel.org/r/9f801e9d8d830408f2ca27821f606e09aa856899.1662078528.git-series.apopple@nvidia.comSigned-off-by: NAlistair Popple <apopple@nvidia.com>
Reported-by: NNadav Amit <nadav.amit@gmail.com>
Reviewed-by: N"Huang, Ying" <ying.huang@intel.com>
Acked-by: NDavid Hildenbrand <david@redhat.com>
Acked-by: NPeter Xu <peterx@redhat.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: huang ying <huang.ying.caritas@gmail.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Karol Herbst <kherbst@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NJialin Zhang <zhangjialin11@huawei.com>
Reviewed-by: NZheng Zengkai <zhengzengkai@huawei.com>

mm/migrate.c

@@ -2471,13 +2471,14 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 		migrate->dst[migrate->npages] = 0;
 		migrate->src[migrate->npages++] = mpfn;
 	}
-	arch_leave_lazy_mmu_mode();
-	pte_unmap_unlock(ptep - 1, ptl);
 
 	/* Only flush the TLB if we actually modified any entries */
 	if (unmapped)
 		flush_tlb_range(walk->vma, start, end);
 
+	arch_leave_lazy_mmu_mode();
+	pte_unmap_unlock(ptep - 1, ptl);
+
 	return 0;
 }