The patch titled
Subject: mm/migrate_device.c: flush TLB while holding PTL
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-migrate_devicec-flush-tlb-while-holding-ptl.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migrate_devicec-flush-tlb-while-holding-ptl.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Alistair Popple <apopple@xxxxxxxxxx>
Subject: mm/migrate_device.c: flush TLB while holding PTL
Date: Fri, 2 Sep 2022 10:35:51 +1000
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@xxxxxxxxxx
Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
Reported-by: Nadav Amit <nadav.amit@xxxxxxxxx>
Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alex Sierra <alex.sierra@xxxxxxx>
Cc: Ben Skeggs <bskeggs@xxxxxxxxxx>
Cc: Felix Kuehling <Felix.Kuehling@xxxxxxx>
Cc: huang ying <huang.ying.caritas@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Karol Herbst <kherbst@xxxxxxxxxx>
Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Cc: Lyude Paul <lyude@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate_device.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/mm/migrate_device.c~mm-migrate_devicec-flush-tlb-while-holding-ptl
+++ a/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;
}
_
Patches currently in -mm which might be from apopple@xxxxxxxxxx are
mm-migrate_devicec-flush-tlb-while-holding-ptl.patch
mm-migrate_devicec-add-missing-flush_cache_page.patch
mm-migrate_devicec-copy-pte-dirty-bit-to-page.patch
mm-gupc-simplify-and-fix-check_and_migrate_movable_pages-return-codes.patch
selftests-hmm-tests-add-test-for-dirty-bits.patch
mm-gupc-dont-pass-gup_flags-to-check_and_migrate_movable_pages.patch
mm-gupc-refactor-check_and_migrate_movable_pages.patch
mm-migrate_devicec-fix-a-misleading-and-out-dated-comment.patch
