On Fri, Oct 12, 2018 at 05:08:33PM +0200, Martin Schwidefsky wrote: > On Thu, 11 Oct 2018 15:02:11 +0200 > Martin Schwidefsky <schwidefsky@xxxxxxxxxx> wrote: > > > On Thu, 11 Oct 2018 18:04:12 +0800 > > Li Wang <liwang@xxxxxxxxxx> wrote: > > > > > When running s390 system with LTP/cve-2017-17052.c[1], the following BUG is > > > came out repeatedly. > > > I remember this warning start from kernel-4.16.0 and now it still exist in > > > kernel-4.19-rc7. > > > Can anyone take a look? > > > > > > [ 2678.991496] BUG: non-zero pgtables_bytes on freeing mm: 16384 > > > [ 2679.001543] BUG: non-zero pgtables_bytes on freeing mm: 16384 > > > [ 2679.002453] BUG: non-zero pgtables_bytes on freeing mm: 16384 > > > [ 2679.003256] BUG: non-zero pgtables_bytes on freeing mm: 16384 > > > [ 2679.013689] BUG: non-zero pgtables_bytes on freeing mm: 16384 > > > [ 2679.024647] BUG: non-zero pgtables_bytes on freeing mm: 16384 > > > [ 2679.064408] BUG: non-zero pgtables_bytes on freeing mm: 16384 > > > [ 2679.133963] BUG: non-zero pgtables_bytes on freeing mm: 16384 > > > > > > [1]: > > > https://github.com/linux-test-project/ltp/blob/master/testcases/cve/cve-2017-17052.c > > > > Confirmed, I see this bug with cvs-2017-17052 on my LPAR as well. > > I'll look into it. > > Ok, I think I understand the problem now. This is the patch I am testing > right now. It seems to fix the issue, but I had to change common mm > code for it. > -- > >From 9e3bc2e96930206ef1ece377e45224c51aca1799 Mon Sep 17 00:00:00 2001 > From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> > Date: Fri, 12 Oct 2018 16:32:29 +0200 > Subject: [RFC][PATCH] s390/mm: fix mis-accounting of pgtable_bytes > > In case a fork or a clone system fails in copy_process and the error > handling does the mmput() at the bad_fork_cleanup_mm label, the following > warning messages will appear on the console: > > BUG: non-zero pgtables_bytes on freeing mm: 16384 > > The reason for that is the tricks we play with mm_inc_nr_puds() and > mm_inc_nr_pmds() in init_new_context(). > > A normal 64-bit process has 3 levels of page table, the p4d level and > the pud level are folded. On process termination the free_pud_range() > function in mm/memory.c will subtract 16KB from pgtable_bytes with a > mm_dec_nr_puds() call, but there actually is not really a pud table. > The s390 version of pud_free_tlb() recognized this an does nothing, > the region-3 table will be freed with the pgd_free() call later on. > But the mm_dec_nr_puds() is done unconditionally, to counter act this > the init_new_context() function has an extra mm_inc_nr_puds() call. > > Now with a failed fork or clone the free_pgtables() function is not > called, there is no mm_dec_nr_puds() but the mm_inc_nr_puds() has > been done which leads to the incorrect pgtable_bytes of 16384. > Nothing is broken by this, but the warning is annoying. > > To get rid of the warning drop the mm_inc_nr_pmds() & mm_inc_nr_puds() > calls from init_new_context(), introduce the mm_pmd_folded(), > pmd_pud_folded() and pmd_p4d_folded() helper, and add if-statements > to the functions mm_[inc|dec]_nr_[pmds|puds]. > > Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> > --- > arch/s390/include/asm/mmu_context.h | 5 ----- > arch/s390/include/asm/pgalloc.h | 6 ++--- > arch/s390/include/asm/pgtable.h | 18 +++++++++++++++ > arch/s390/include/asm/tlb.h | 6 ++--- > include/linux/mm.h | 44 ++++++++++++++++++++++++++++++++----- > 5 files changed, 62 insertions(+), 17 deletions(-) > > diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h > index dbd689d556ce..ccbb53e22024 100644 > --- a/arch/s390/include/asm/mmu_context.h > +++ b/arch/s390/include/asm/mmu_context.h > @@ -46,8 +46,6 @@ static inline int init_new_context(struct task_struct *tsk, > mm->context.asce_limit = STACK_TOP_MAX; > mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | > _ASCE_USER_BITS | _ASCE_TYPE_REGION3; > - /* pgd_alloc() did not account this pud */ > - mm_inc_nr_puds(mm); > break; > case -PAGE_SIZE: > /* forked 5-level task, set new asce with new_mm->pgd */ > @@ -63,9 +61,6 @@ static inline int init_new_context(struct task_struct *tsk, > /* forked 2-level compat task, set new asce with new mm->pgd */ > mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | > _ASCE_USER_BITS | _ASCE_TYPE_SEGMENT; > - /* pgd_alloc() did not account this pmd */ > - mm_inc_nr_pmds(mm); > - mm_inc_nr_puds(mm); > } > crst_table_init((unsigned long *) mm->pgd, pgd_entry_type(mm)); > return 0; > diff --git a/arch/s390/include/asm/pgalloc.h b/arch/s390/include/asm/pgalloc.h > index f0f9bcf94c03..5ee733720a57 100644 > --- a/arch/s390/include/asm/pgalloc.h > +++ b/arch/s390/include/asm/pgalloc.h > @@ -36,11 +36,11 @@ static inline void crst_table_init(unsigned long *crst, unsigned long entry) > > static inline unsigned long pgd_entry_type(struct mm_struct *mm) > { > - if (mm->context.asce_limit <= _REGION3_SIZE) > + if (mm_pmd_folded(mm)) > return _SEGMENT_ENTRY_EMPTY; > - if (mm->context.asce_limit <= _REGION2_SIZE) > + if (mm_pud_folded(mm)) > return _REGION3_ENTRY_EMPTY; > - if (mm->context.asce_limit <= _REGION1_SIZE) > + if (mm_p4d_folded(mm)) > return _REGION2_ENTRY_EMPTY; > return _REGION1_ENTRY_EMPTY; > } > diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h > index 411d435e7a7d..063732414dfb 100644 > --- a/arch/s390/include/asm/pgtable.h > +++ b/arch/s390/include/asm/pgtable.h > @@ -493,6 +493,24 @@ static inline int is_module_addr(void *addr) > _REGION_ENTRY_PROTECT | \ > _REGION_ENTRY_NOEXEC) > > +static inline bool mm_p4d_folded(struct mm_struct *mm) > +{ > + return mm->context.asce_limit <= _REGION1_SIZE; > +} > +#define mm_p4d_folded(mm) mm_p4d_folded(mm) > + > +static inline bool mm_pud_folded(struct mm_struct *mm) > +{ > + return mm->context.asce_limit <= _REGION2_SIZE; > +} > +#define mm_pud_folded(mm) mm_pud_folded(mm) > + > +static inline bool mm_pmd_folded(struct mm_struct *mm) > +{ > + return mm->context.asce_limit <= _REGION3_SIZE; > +} > +#define mm_pmd_folded(mm) mm_pmd_folded(mm) > + > static inline int mm_has_pgste(struct mm_struct *mm) > { > #ifdef CONFIG_PGSTE > diff --git a/arch/s390/include/asm/tlb.h b/arch/s390/include/asm/tlb.h > index 457b7ba0fbb6..b31c779cf581 100644 > --- a/arch/s390/include/asm/tlb.h > +++ b/arch/s390/include/asm/tlb.h > @@ -136,7 +136,7 @@ static inline void pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, > static inline void pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd, > unsigned long address) > { > - if (tlb->mm->context.asce_limit <= _REGION3_SIZE) > + if (mm_pmd_folded(tlb->mm)) > return; > pgtable_pmd_page_dtor(virt_to_page(pmd)); > tlb_remove_table(tlb, pmd); > @@ -152,7 +152,7 @@ static inline void pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd, > static inline void p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d, > unsigned long address) > { > - if (tlb->mm->context.asce_limit <= _REGION1_SIZE) > + if (mm_p4d_folded(tlb->mm)) > return; > tlb_remove_table(tlb, p4d); > } > @@ -167,7 +167,7 @@ static inline void p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d, > static inline void pud_free_tlb(struct mmu_gather *tlb, pud_t *pud, > unsigned long address) > { > - if (tlb->mm->context.asce_limit <= _REGION2_SIZE) > + if (mm_pud_folded(tlb->mm)) > return; > tlb_remove_table(tlb, pud); > } > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 0416a7204be3..1e4a045f19ec 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -105,6 +105,34 @@ extern int mmap_rnd_compat_bits __read_mostly; > #define mm_zero_struct_page(pp) ((void)memset((pp), 0, sizeof(struct page))) > #endif > > +/* > + * On some architectures it depends on the mm if the p4d/pud or pmd > + * layer of the page table hierarchy is folded or not. > + */ > +#ifndef mm_p4d_folded > +#define mm_p4d_folded(mm) mm_p4d_folded(mm) > +static inline bool mm_p4d_folded(struct mm_struct *mm) > +{ > + return __is_defined(__PAGETABLE_P4D_FOLDED); > +} > +#endif > + > +#ifndef mm_pud_folded > +#define mm_pud_folded(mm) mm_pud_folded(mm) > +static inline bool mm_pud_folded(struct mm_struct *mm) > +{ > + return __is_defined(__PAGETABLE_PUD_FOLDED); > +} > +#endif > + > +#ifndef mm_pmd_folded > +#define mm_pmd_folded(mm) mm_pmd_folded(mm) > +static inline bool mm_pmd_folded(struct mm_struct *mm) > +{ > + return __is_defined(__PAGETABLE_PMD_FOLDED); > +} > +#endif > + > /* > * Default maximum number of active map areas, this limits the number of vmas > * per mm struct. Users can overwrite this number by sysctl but there is a > @@ -1710,7 +1738,7 @@ static inline int __p4d_alloc(struct mm_struct *mm, pgd_t *pgd, > int __p4d_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address); > #endif > > -#if defined(__PAGETABLE_PUD_FOLDED) || !defined(CONFIG_MMU) > +#if !defined(CONFIG_MMU) > static inline int __pud_alloc(struct mm_struct *mm, p4d_t *p4d, > unsigned long address) > { > @@ -1724,16 +1752,18 @@ int __pud_alloc(struct mm_struct *mm, p4d_t *p4d, unsigned long address); > > static inline void mm_inc_nr_puds(struct mm_struct *mm) > { > - atomic_long_add(PTRS_PER_PUD * sizeof(pud_t), &mm->pgtables_bytes); > + if (!mm_pud_folded(mm)) > + atomic_long_add(PTRS_PER_PUD * sizeof(pud_t), &mm->pgtables_bytes); > } > > static inline void mm_dec_nr_puds(struct mm_struct *mm) > { > - atomic_long_sub(PTRS_PER_PUD * sizeof(pud_t), &mm->pgtables_bytes); > + if (!mm_pud_folded(mm)) > + atomic_long_sub(PTRS_PER_PUD * sizeof(pud_t), &mm->pgtables_bytes); > } > #endif > > -#if defined(__PAGETABLE_PMD_FOLDED) || !defined(CONFIG_MMU) > +#if !defined(CONFIG_MMU) > static inline int __pmd_alloc(struct mm_struct *mm, pud_t *pud, > unsigned long address) > { > @@ -1748,12 +1778,14 @@ int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address); > > static inline void mm_inc_nr_pmds(struct mm_struct *mm) > { > - atomic_long_add(PTRS_PER_PMD * sizeof(pmd_t), &mm->pgtables_bytes); > + if (!mm_pmd_folded(mm)) > + atomic_long_add(PTRS_PER_PMD * sizeof(pmd_t), &mm->pgtables_bytes); > } > > static inline void mm_dec_nr_pmds(struct mm_struct *mm) > { > - atomic_long_sub(PTRS_PER_PMD * sizeof(pmd_t), &mm->pgtables_bytes); > + if (!mm_pmd_folded(mm)) > + atomic_long_sub(PTRS_PER_PMD * sizeof(pmd_t), &mm->pgtables_bytes); > } > #endif > > -- > 2.16.4 > > > -- Hi Martin, We've seen these "non-zero pgtable byte" complaints as well and I found this thread + test patch. Looks good after applying and running the LTP cve-2017-17052 test over here. Did this need further testing and/or review? I didn't see it in the kernel/git/s390/linux.git tree so I thought I would ask. Thanks, -- Joe
