On Wed, 31 Oct 2018 15:57:54 -0400 Joe Lawrence <joe.lawrence@xxxxxxxxxx> wrote: > 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 I have sent a v3 of these patches and got some Acked-by from Kirill. Waited for a few days and as there are no more comments, I will now add them to the linux-s390 tree. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.
