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mm: fix gup_pud_range

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sorry for not processing for a long time.  I met it again.

patch v1   https://lkml.org/lkml/2019/9/20/656

do_machine_check()
  do_memory_failure()
    memory_failure()
      hw_poison_user_mappings()
        try_to_unmap()
          pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));

...and now we have a swap entry that indicates that the page entry
refers to a bad (and poisoned) page of memory, but gup_fast() at this
level of the page table was ignoring swap entries, and incorrectly
assuming that "!pxd_none() == valid and present".

And this was not just a poisoned page problem, but a generaly swap entry
problem.  So, any swap entry type (device memory migration, numa
migration, or just regular swapping) could lead to the same problem.

Fix this by checking for pxd_present(), instead of pxd_none().

Link: http://lkml.kernel.org/r/1578479084-15508-1-git-send-email-hqjagain@gmail.com
Signed-off-by: Qiujun Huang <hqjagain@gmail.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Qiujun Huang 2020-01-30 22:12:10 -08:00 • committed by Linus Torvalds
commit 15494520b7
1 changed files with 1 additions and 1 deletions
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