Commit 6bdb913f0a70a4dfb7f066fb15e2d6f960701d00 (mm: wrap calls to set_pte_at_notify with invalidate_range_start and invalidate_range_end) breaks semantics of set_pte_at_notify. When calls to set_pte_at_notify are wrapped with mmu_notifier_invalidate_range_start and mmu_notifier_invalidate_range_end, KVM zaps pte during mmu_notifier_invalidate_range_start callback and set_pte_at_notify has no spte to update and therefore it's called for nothing.
As Andrea suggested (1), the problem is resolved by calling mmu_notifier_invalidate_page after PT lock has been released and only for mmu_notifiers that do not implement change_ptr callback. (1) http://thread.gmane.org/gmane.linux.kernel.mm/111710/focus=111711 Reported-by: Izik Eidus <[email protected]> Signed-off-by: Mike Rapoport <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: Haggai Eran <[email protected]> Cc: Peter Zijlstra <[email protected]> --- include/linux/mmu_notifier.h | 31 ++++++++++++++++++++++++++----- kernel/events/uprobes.c | 12 ++++++------ mm/ksm.c | 15 +++++---------- mm/memory.c | 14 +++++--------- mm/mmu_notifier.c | 24 ++++++++++++++++++++++-- 5 files changed, 64 insertions(+), 32 deletions(-) diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h index deca874..46c96cb 100644 --- a/include/linux/mmu_notifier.h +++ b/include/linux/mmu_notifier.h @@ -176,14 +176,17 @@ extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm, unsigned long address); extern int __mmu_notifier_test_young(struct mm_struct *mm, unsigned long address); -extern void __mmu_notifier_change_pte(struct mm_struct *mm, - unsigned long address, pte_t pte); +extern int __mmu_notifier_change_pte(struct mm_struct *mm, + unsigned long address, pte_t pte); extern void __mmu_notifier_invalidate_page(struct mm_struct *mm, unsigned long address); extern void __mmu_notifier_invalidate_range_start(struct mm_struct *mm, unsigned long start, unsigned long end); extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm, unsigned long start, unsigned long end); +extern void +__mmu_notifier_invalidate_page_if_missing_change_pte(struct mm_struct *mm, + unsigned long address); static inline void mmu_notifier_release(struct mm_struct *mm) { @@ -207,11 +210,12 @@ static inline int mmu_notifier_test_young(struct mm_struct *mm, return 0; } -static inline void mmu_notifier_change_pte(struct mm_struct *mm, +static inline int mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address, pte_t pte) { if (mm_has_notifiers(mm)) - __mmu_notifier_change_pte(mm, address, pte); + return __mmu_notifier_change_pte(mm, address, pte); + return 0; } static inline void mmu_notifier_invalidate_page(struct mm_struct *mm, @@ -235,6 +239,15 @@ static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm, __mmu_notifier_invalidate_range_end(mm, start, end); } +static inline +void mmu_notifier_invalidate_page_if_missing_change_pte(struct mm_struct *mm, + unsigned long address) +{ + if (mm_has_notifiers(mm)) + __mmu_notifier_invalidate_page_if_missing_change_pte(mm, + address); +} + static inline void mmu_notifier_mm_init(struct mm_struct *mm) { mm->mmu_notifier_mm = NULL; @@ -283,9 +296,11 @@ static inline void mmu_notifier_mm_destroy(struct mm_struct *mm) struct mm_struct *___mm = __mm; \ unsigned long ___address = __address; \ pte_t ___pte = __pte; \ + int ___ret; \ \ - mmu_notifier_change_pte(___mm, ___address, ___pte); \ + ___ret = mmu_notifier_change_pte(___mm, ___address, ___pte); \ set_pte_at(___mm, ___address, __ptep, ___pte); \ + ___ret; \ }) #else /* CONFIG_MMU_NOTIFIER */ @@ -326,6 +341,12 @@ static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm, { } +static inline +void mmu_notifier_invalidate_page_if_missing_change_pte(struct mm_struct *mm, + unsigned long address) +{ +} + static inline void mmu_notifier_mm_init(struct mm_struct *mm) { } diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 24b7d6c..ec49338 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -131,14 +131,11 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr, spinlock_t *ptl; pte_t *ptep; int err; - /* For mmu_notifiers */ - const unsigned long mmun_start = addr; - const unsigned long mmun_end = addr + PAGE_SIZE; + int notify_missing = 0; /* For try_to_free_swap() and munlock_vma_page() below */ lock_page(page); - mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); err = -EAGAIN; ptep = page_check_address(page, mm, addr, &ptl, 0); if (!ptep) @@ -154,20 +151,23 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr, flush_cache_page(vma, addr, pte_pfn(*ptep)); ptep_clear_flush(vma, addr, ptep); - set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); + notify_missing = set_pte_at_notify(mm, addr, ptep, + mk_pte(kpage, vma->vm_page_prot)); page_remove_rmap(page); if (!page_mapped(page)) try_to_free_swap(page); pte_unmap_unlock(ptep, ptl); + if (notify_missing) + mmu_notifier_invalidate_page_if_missing_change_pte(mm, addr); + if (vma->vm_flags & VM_LOCKED) munlock_vma_page(page); put_page(page); err = 0; unlock: - mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); unlock_page(page); return err; } diff --git a/mm/ksm.c b/mm/ksm.c index 175fff7..42e8254 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -861,8 +861,7 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page, spinlock_t *ptl; int swapped; int err = -EFAULT; - unsigned long mmun_start; /* For mmu_notifiers */ - unsigned long mmun_end; /* For mmu_notifiers */ + int notify_missing = 0; addr = page_address_in_vma(page, vma); if (addr == -EFAULT) @@ -870,13 +869,9 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page, BUG_ON(PageTransCompound(page)); - mmun_start = addr; - mmun_end = addr + PAGE_SIZE; - mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); - ptep = page_check_address(page, mm, addr, &ptl, 0); if (!ptep) - goto out_mn; + goto out; if (pte_write(*ptep) || pte_dirty(*ptep)) { pte_t entry; @@ -904,15 +899,15 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page, if (pte_dirty(entry)) set_page_dirty(page); entry = pte_mkclean(pte_wrprotect(entry)); - set_pte_at_notify(mm, addr, ptep, entry); + notify_missing = set_pte_at_notify(mm, addr, ptep, entry); } *orig_pte = *ptep; err = 0; out_unlock: pte_unmap_unlock(ptep, ptl); -out_mn: - mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + if (notify_missing) + mmu_notifier_invalidate_page_if_missing_change_pte(mm, addr); out: return err; } diff --git a/mm/memory.c b/mm/memory.c index 6768ce9..596d4c3 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2611,8 +2611,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, int ret = 0; int page_mkwrite = 0; struct page *dirty_page = NULL; - unsigned long mmun_start = 0; /* For mmu_notifiers */ - unsigned long mmun_end = 0; /* For mmu_notifiers */ + int notify_missing = 0; old_page = vm_normal_page(vma, address, orig_pte); if (!old_page) { @@ -2798,10 +2797,6 @@ gotten: if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)) goto oom_free_new; - mmun_start = address & PAGE_MASK; - mmun_end = mmun_start + PAGE_SIZE; - mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); - /* * Re-check the pte - we dropped the lock */ @@ -2830,7 +2825,8 @@ gotten: * mmu page tables (such as kvm shadow page tables), we want the * new page to be mapped directly into the secondary page table. */ - set_pte_at_notify(mm, address, page_table, entry); + notify_missing = set_pte_at_notify(mm, address, page_table, + entry); update_mmu_cache(vma, address, page_table); if (old_page) { /* @@ -2868,8 +2864,8 @@ gotten: page_cache_release(new_page); unlock: pte_unmap_unlock(page_table, ptl); - if (mmun_end > mmun_start) - mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + if (notify_missing) + mmu_notifier_invalidate_page_if_missing_change_pte(mm, address); if (old_page) { /* * Don't let another task, with possibly unlocked vma, diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c index 93e6089..5fc5bc2 100644 --- a/mm/mmu_notifier.c +++ b/mm/mmu_notifier.c @@ -122,18 +122,23 @@ int __mmu_notifier_test_young(struct mm_struct *mm, return young; } -void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address, - pte_t pte) +int __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address, + pte_t pte) { struct mmu_notifier *mn; int id; + int ret = 0; id = srcu_read_lock(&srcu); hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { if (mn->ops->change_pte) mn->ops->change_pte(mn, mm, address, pte); + else + ret = 1; } srcu_read_unlock(&srcu, id); + + return ret; } void __mmu_notifier_invalidate_page(struct mm_struct *mm, @@ -180,6 +185,21 @@ void __mmu_notifier_invalidate_range_end(struct mm_struct *mm, } EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end); +void __mmu_notifier_invalidate_page_if_missing_change_pte(struct mm_struct *mm, + unsigned long address) +{ + struct mmu_notifier *mn; + int id; + + id = srcu_read_lock(&srcu); + hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { + if (mn->ops->invalidate_page && !mn->ops->change_pte) + mn->ops->invalidate_page(mn, mm, address); + } + srcu_read_unlock(&srcu, id); +} +EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_page_if_missing_change_pte); + static int do_mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm, int take_mmap_sem) -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
