diff options
| author | Minchan Kim <minchan@kernel.org> | 2015-10-22 13:32:19 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-11-09 14:37:39 -0800 |
| commit | eda9ff7378eafa57603efc19a0312ef5b2142124 (patch) | |
| tree | 24b956ead54d9b65fc3f3221ea2719f900095694 | |
| parent | 683b2b86aceed0df49641a1c34d56da7aa104823 (diff) | |
thp: use is_zero_pfn() only after pte_present() check
commit 47aee4d8e314384807e98b67ade07f6da476aa75 upstream.
Use is_zero_pfn() on pteval only after pte_present() check on pteval
(It might be better idea to introduce is_zero_pte() which checks
pte_present() first).
Otherwise when working on a swap or migration entry and if pte_pfn's
result is equal to zero_pfn by chance, we lose user's data in
__collapse_huge_page_copy(). So if you're unlucky, the application
segfaults and finally you could see below message on exit:
BUG: Bad rss-counter state mm:ffff88007f099300 idx:2 val:3
Fixes: ca0984caa823 ("mm: incorporate zero pages into transparent huge pages")
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | mm/huge_memory.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 097c7a4bfbd9..da0ac6a0445f 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2132,7 +2132,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++, address += PAGE_SIZE) { pte_t pteval = *_pte; - if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { + if (pte_none(pteval) || (pte_present(pteval) && + is_zero_pfn(pte_pfn(pteval)))) { if (++none_or_zero <= khugepaged_max_ptes_none) continue; else |