From: Alistair Popple apopple@nvidia.com
commit 60bae73708963de4a17231077285bd9ff2f41c44 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: 8c3328f1f36a ("mm/migrate: migrate_vma() unmap page from vma while collecting pages") Link: https://lkml.kernel.org/r/9f801e9d8d830408f2ca27821f606e09aa856899.166207852... Signed-off-by: Alistair Popple apopple@nvidia.com Reported-by: Nadav Amit nadav.amit@gmail.com Reviewed-by: "Huang, Ying" ying.huang@intel.com Acked-by: David Hildenbrand david@redhat.com Acked-by: Peter 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: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/migrate.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/mm/migrate.c +++ b/mm/migrate.c @@ -2343,13 +2343,14 @@ 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; }