From 60bae73708963de4a17231077285bd9ff2f41c44 Mon Sep 17 00:00:00 2001 From: Alistair Popple Date: Fri, 2 Sep 2022 10:35:51 +1000 Subject: mm/migrate_device.c: flush TLB while holding PTL 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 Reported-by: Nadav Amit Reviewed-by: "Huang, Ying" Acked-by: David Hildenbrand Acked-by: Peter Xu Cc: Alex Sierra Cc: Ben Skeggs Cc: Felix Kuehling Cc: huang ying Cc: Jason Gunthorpe Cc: John Hubbard Cc: Karol Herbst Cc: Logan Gunthorpe Cc: Lyude Paul Cc: Matthew Wilcox Cc: Paul Mackerras Cc: Ralph Campbell Cc: Signed-off-by: Andrew Morton --- mm/migrate_device.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'mm/migrate_device.c') diff --git a/mm/migrate_device.c b/mm/migrate_device.c index 27fb37d65476..6a5ef9f0da6a 100644 --- a/mm/migrate_device.c +++ b/mm/migrate_device.c @@ -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; } -- cgit v1.2.3