]> Git Repo - linux.git/commitdiff
mm/migrate_device.c: flush TLB while holding PTL
authorAlistair Popple <[email protected]>
Fri, 2 Sep 2022 00:35:51 +0000 (10:35 +1000)
committerAndrew Morton <[email protected]>
Sun, 11 Sep 2022 23:22:30 +0000 (16:22 -0700)
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: 8c3328f1f36a ("mm/migrate: migrate_vma() unmap page from vma while collecting pages")
Link: https://lkml.kernel.org/r/9f801e9d8d830408f2ca27821f606e09aa856899.1662078528.git-series.apopple@nvidia.com
Signed-off-by: Alistair Popple <[email protected]>
Reported-by: Nadav Amit <[email protected]>
Reviewed-by: "Huang, Ying" <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Acked-by: Peter Xu <[email protected]>
Cc: Alex Sierra <[email protected]>
Cc: Ben Skeggs <[email protected]>
Cc: Felix Kuehling <[email protected]>
Cc: huang ying <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Karol Herbst <[email protected]>
Cc: Logan Gunthorpe <[email protected]>
Cc: Lyude Paul <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Ralph Campbell <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
mm/migrate_device.c

index 27fb37d65476c24a3103a6c3cf830f4982255c7d..6a5ef9f0da6a2ffaf19f21c10edfd9d1f9863bd7 100644 (file)
@@ -254,13 +254,14 @@ next:
                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;
 }
 
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