The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 1bd3d9c593211e09771562b464028d3ab7e05b3a
Gitweb: https://git.kernel.org/tip/1bd3d9c593211e09771562b464028d3ab7e05b3a
Author: Dan Williams <dan.j.williams@xxxxxxxxx>
AuthorDate: Wed, 02 Dec 2020 22:28:12 -08:00
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Tue, 05 Jan 2021 11:17:21 +01:00
x86/mm: Fix leak of pmd ptlock
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@xxxxxxxxxxxxx>.
Fixes: 28ee90fe6048 ("x86/mm: implement free pmd/pte page interfaces")
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Tested-by: Yi Zhang <yi.zhang@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/160697689204.605323.17629854984697045602.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
---
arch/x86/mm/pgtable.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index dfd82f5..f6a9e2e 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -829,6 +829,8 @@ int pud_free_pmd_page(pud_t *pud, unsigned long addr)
}
free_page((unsigned long)pmd_sv);
+
+ pgtable_pmd_page_dtor(virt_to_page(pmd));
free_page((unsigned long)pmd);
return 1;
|