From: Dan Williams dan.j.williams@intel.com
commit d1c5246e08eb64991001d97a3bd119c93edbc79a upstream.
Commit
28ee90fe6048 ("x86/mm: implement free pmd/pte page interfaces")
introduced a new location where a pmd was released, but neglected to run the pmd page destructor. In fact, this happened previously for a different pmd release path and was fixed by commit:
c283610e44ec ("x86, mm: do not leak page->ptl for pmd page tables").
This issue was hidden until recently because the failure mode is silent, but commit:
b2b29d6d0119 ("mm: account PMD tables like PTE tables")
turns the failure mode into this signature:
BUG: Bad page state in process lt-pmem-ns pfn:15943d page:000000007262ed7b refcount:0 mapcount:-1024 mapping:0000000000000000 index:0x0 pfn:0x15943d flags: 0xaffff800000000() raw: 00affff800000000 dead000000000100 0000000000000000 0000000000000000 raw: 0000000000000000 ffff913a029bcc08 00000000fffffbff 0000000000000000 page dumped because: nonzero mapcount [..] dump_stack+0x8b/0xb0 bad_page.cold+0x63/0x94 free_pcp_prepare+0x224/0x270 free_unref_page+0x18/0xd0 pud_free_pmd_page+0x146/0x160 ioremap_pud_range+0xe3/0x350 ioremap_page_range+0x108/0x160 __ioremap_caller.constprop.0+0x174/0x2b0 ? memremap+0x7a/0x110 memremap+0x7a/0x110 devm_memremap+0x53/0xa0 pmem_attach_disk+0x4ed/0x530 [nd_pmem] ? __devm_release_region+0x52/0x80 nvdimm_bus_probe+0x85/0x210 [libnvdimm]
Given this is a repeat occurrence it seemed prudent to look for other places where this destructor might be missing and whether a better helper is needed. try_to_free_pmd_page() looks like a candidate, but testing with setting up and tearing down pmd mappings via the dax unit tests is thus far not triggering the failure.
As for a better helper pmd_free() is close, but it is a messy fit due to requiring an @mm arg. Also, ___pmd_free_tlb() wants to call paravirt_tlb_remove_table() instead of free_page(), so open-coded pgtable_pmd_page_dtor() seems the best way forward for now.
Debugged together with Matthew Wilcox willy@infradead.org.
Fixes: 28ee90fe6048 ("x86/mm: implement free pmd/pte page interfaces") Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Borislav Petkov bp@suse.de Tested-by: Yi Zhang yi.zhang@redhat.com Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/160697689204.605323.17629854984697045602.stgit@dwi... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/mm/pgtable.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -826,6 +826,8 @@ int pud_free_pmd_page(pud_t *pud, unsign }
free_page((unsigned long)pmd_sv); + + pgtable_pmd_page_dtor(virt_to_page(pmd)); free_page((unsigned long)pmd);
return 1;