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mm/page_table_check: fix crash on ZONE_DEVICE
commit8bb592c2ec
upstream. Not all pages may apply to pgtable check. One example is ZONE_DEVICE pages: they map PFNs directly, and they don't allocate page_ext at all even if there's struct page around. One may reference devm_memremap_pages(). When both ZONE_DEVICE and page-table-check enabled, then try to map some dax memories, one can trigger kernel bug constantly now when the kernel was trying to inject some pfn maps on the dax device: kernel BUG at mm/page_table_check.c:55! While it's pretty legal to use set_pxx_at() for ZONE_DEVICE pages for page fault resolutions, skip all the checks if page_ext doesn't even exist in pgtable checker, which applies to ZONE_DEVICE but maybe more. Link: https://lkml.kernel.org/r/20240605212146.994486-1-peterx@redhat.com Fixes:df4e817b71
("mm: page table check") Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Reviewed-by: Alistair Popple <apopple@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>
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1 changed files with 10 additions and 1 deletions
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@ -71,6 +71,9 @@ static void page_table_check_clear(unsigned long pfn, unsigned long pgcnt)
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page = pfn_to_page(pfn);
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page_ext = page_ext_get(page);
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if (!page_ext)
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return;
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BUG_ON(PageSlab(page));
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anon = PageAnon(page);
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@ -108,6 +111,9 @@ static void page_table_check_set(unsigned long pfn, unsigned long pgcnt,
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page = pfn_to_page(pfn);
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page_ext = page_ext_get(page);
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if (!page_ext)
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return;
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BUG_ON(PageSlab(page));
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anon = PageAnon(page);
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@ -138,7 +144,10 @@ void __page_table_check_zero(struct page *page, unsigned int order)
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BUG_ON(PageSlab(page));
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page_ext = page_ext_get(page);
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BUG_ON(!page_ext);
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if (!page_ext)
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return;
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for (i = 0; i < (1ul << order); i++) {
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struct page_table_check *ptc = get_page_table_check(page_ext);
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