Messages in this thread | | | Date | Mon, 21 Nov 2022 18:18:59 +0000 | From | Will Deacon <> | Subject | Re: [PATCH v3] arm64/mm: fix incorrect file_map_count for invalid pmd |
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On Mon, Nov 21, 2022 at 03:36:08PM +0800, Liu Shixin wrote: > The page table check trigger BUG_ON() unexpectedly when split hugepage: > > ------------[ cut here ]------------ > kernel BUG at mm/page_table_check.c:119! > Internal error: Oops - BUG: 00000000f2000800 [#1] SMP > Dumping ftrace buffer: > (ftrace buffer empty) > Modules linked in: > CPU: 7 PID: 210 Comm: transhuge-stres Not tainted 6.1.0-rc3+ #748 > Hardware name: linux,dummy-virt (DT) > pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : page_table_check_set.isra.0+0x398/0x468 > lr : page_table_check_set.isra.0+0x1c0/0x468 > [...] > Call trace: > page_table_check_set.isra.0+0x398/0x468 > __page_table_check_pte_set+0x160/0x1c0 > __split_huge_pmd_locked+0x900/0x1648 > __split_huge_pmd+0x28c/0x3b8 > unmap_page_range+0x428/0x858 > unmap_single_vma+0xf4/0x1c8 > zap_page_range+0x2b0/0x410 > madvise_vma_behavior+0xc44/0xe78 > do_madvise+0x280/0x698 > __arm64_sys_madvise+0x90/0xe8 > invoke_syscall.constprop.0+0xdc/0x1d8 > do_el0_svc+0xf4/0x3f8 > el0_svc+0x58/0x120 > el0t_64_sync_handler+0xb8/0xc0 > el0t_64_sync+0x19c/0x1a0 > [...] > > On arm64, pmd_leaf() will return true even if the pmd is invalid due to > pmd_present_invalid() check. So in pmdp_invalidate() the file_map_count > will not only decrease once but also increase once. Then in set_pte_at(), > the file_map_count increase again, and so trigger BUG_ON() unexpectedly. > > Add !pmd_present_invalid() check in pmd_user_accessible_page() to fix the > problem. > > Fixes: 42b2547137f5 ("arm64/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK") > Reported-by: Denys Vlasenko <dvlasenk@redhat.com> > Signed-off-by: Liu Shixin <liushixin2@huawei.com> > Acked-by: Pasha Tatashin <pasha.tatashin@soleen.com> > Acked-by: David Hildenbrand <david@redhat.com> > Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> > --- > v1->v2: Update comment and optimize the code by moving p?d_valid() at > first place suggested by Mark. > v2->v3: Replace pmd_valid() with pmd_present_invalid() suggested by Will. > > arch/arm64/include/asm/pgtable.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index edf6625ce965..17afb09f386f 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -863,7 +863,7 @@ static inline bool pte_user_accessible_page(pte_t pte) > > static inline bool pmd_user_accessible_page(pmd_t pmd) > { > - return pmd_leaf(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd)); > + return pmd_leaf(pmd) && !pmd_present_invalid(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd)); > }
Acked-by: Will Deacon <will@kernel.org>
But please see my comment on v2 about pud_user_exec() for the PUD case.
Will
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