From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Nadav Amit To: CC: , , , , Minchan Kim , , Nadav Amit Subject: [PATCH v4 1/3] mm: migrate: prevent racy access to tlb_flush_pending Date: Mon, 31 Jul 2017 03:42:47 -0700 Message-ID: <20170731104249.233458-2-namit@vmware.com> In-Reply-To: <20170731104249.233458-1-namit@vmware.com> References: <20170731104249.233458-1-namit@vmware.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: From: Nadav Amit Setting and clearing mm->tlb_flush_pending can be performed by multiple threads, since mmap_sem may only be acquired for read in task_numa_work(). If this happens, tlb_flush_pending might be cleared while one of the threads still changes PTEs and batches TLB flushes. This can lead to the same race between migration and change_protection_range() that led to the introduction of tlb_flush_pending. The result of this race was data corruption, which means that this patch also addresses a theoretically possible data corruption. An actual data corruption was not observed, yet the race was was confirmed by adding assertion to check tlb_flush_pending is not set by two threads, adding artificial latency in change_protection_range() and using sysctl to reduce kernel.numa_balancing_scan_delay_ms. Fixes: 20841405940e ("mm: fix TLB flush race between migration, and change_protection_range") Cc: Minchan Kim Cc: Andy Lutomirski Cc: stable@vger.kernel.org Signed-off-by: Nadav Amit Acked-by: Mel Gorman Acked-by: Rik van Riel --- include/linux/mm_types.h | 31 ++++++++++++++++++++++--------- kernel/fork.c | 2 +- mm/debug.c | 2 +- mm/mprotect.c | 4 ++-- 4 files changed, 26 insertions(+), 13 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 45cdb27791a3..f5263dd0f1bc 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -493,7 +493,7 @@ struct mm_struct { * can move process memory needs to flush the TLB when moving a * PROT_NONE or PROT_NUMA mapped page. */ - bool tlb_flush_pending; + atomic_t tlb_flush_pending; #endif struct uprobes_state uprobes_state; #ifdef CONFIG_HUGETLB_PAGE @@ -528,33 +528,46 @@ static inline cpumask_t *mm_cpumask(struct mm_struct *mm) static inline bool mm_tlb_flush_pending(struct mm_struct *mm) { barrier(); - return mm->tlb_flush_pending; + return atomic_read(&mm->tlb_flush_pending) > 0; } -static inline void set_tlb_flush_pending(struct mm_struct *mm) + +static inline void init_tlb_flush_pending(struct mm_struct *mm) { - mm->tlb_flush_pending = true; + atomic_set(&mm->tlb_flush_pending, 0); +} + +static inline void inc_tlb_flush_pending(struct mm_struct *mm) +{ + atomic_inc(&mm->tlb_flush_pending); /* - * Guarantee that the tlb_flush_pending store does not leak into the + * Guarantee that the tlb_flush_pending increase does not leak into the * critical section updating the page tables */ smp_mb__before_spinlock(); } + /* Clearing is done after a TLB flush, which also provides a barrier. */ -static inline void clear_tlb_flush_pending(struct mm_struct *mm) +static inline void dec_tlb_flush_pending(struct mm_struct *mm) { barrier(); - mm->tlb_flush_pending = false; + atomic_dec(&mm->tlb_flush_pending); } #else static inline bool mm_tlb_flush_pending(struct mm_struct *mm) { return false; } -static inline void set_tlb_flush_pending(struct mm_struct *mm) + +static inline void init_tlb_flush_pending(struct mm_struct *mm) { } -static inline void clear_tlb_flush_pending(struct mm_struct *mm) + +static inline void inc_tlb_flush_pending(struct mm_struct *mm) +{ +} + +static inline void dec_tlb_flush_pending(struct mm_struct *mm) { } #endif diff --git a/kernel/fork.c b/kernel/fork.c index e53770d2bf95..840e7a7132e1 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -809,7 +809,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, mm_init_aio(mm); mm_init_owner(mm, p); mmu_notifier_mm_init(mm); - clear_tlb_flush_pending(mm); + init_tlb_flush_pending(mm); #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS mm->pmd_huge_pte = NULL; #endif diff --git a/mm/debug.c b/mm/debug.c index db1cd26d8752..d70103bb4731 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -159,7 +159,7 @@ void dump_mm(const struct mm_struct *mm) mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq, #endif #if defined(CONFIG_NUMA_BALANCING) || defined(CONFIG_COMPACTION) - mm->tlb_flush_pending, + atomic_read(&mm->tlb_flush_pending), #endif mm->def_flags, &mm->def_flags ); diff --git a/mm/mprotect.c b/mm/mprotect.c index 8edd0d576254..0c413774c1e3 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -245,7 +245,7 @@ static unsigned long change_protection_range(struct vm_area_struct *vma, BUG_ON(addr >= end); pgd = pgd_offset(mm, addr); flush_cache_range(vma, addr, end); - set_tlb_flush_pending(mm); + inc_tlb_flush_pending(mm); do { next = pgd_addr_end(addr, end); if (pgd_none_or_clear_bad(pgd)) @@ -257,7 +257,7 @@ static unsigned long change_protection_range(struct vm_area_struct *vma, /* Only flush the TLB if we actually modified any entries: */ if (pages) flush_tlb_range(vma, start, end); - clear_tlb_flush_pending(mm); + dec_tlb_flush_pending(mm); return pages; } -- 2.11.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id C44FB6B04B0 for ; Mon, 31 Jul 2017 13:52:28 -0400 (EDT) Received: by mail-pg0-f71.google.com with SMTP id t80so10473726pgb.0 for ; Mon, 31 Jul 2017 10:52:28 -0700 (PDT) Received: from EX13-EDG-OU-001.vmware.com (ex13-edg-ou-001.vmware.com. [208.91.0.189]) by mx.google.com with ESMTPS id f67si16383061pfg.687.2017.07.31.10.52.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 31 Jul 2017 10:52:27 -0700 (PDT) From: Nadav Amit Subject: [PATCH v4 1/3] mm: migrate: prevent racy access to tlb_flush_pending Date: Mon, 31 Jul 2017 03:42:47 -0700 Message-ID: <20170731104249.233458-2-namit@vmware.com> In-Reply-To: <20170731104249.233458-1-namit@vmware.com> References: <20170731104249.233458-1-namit@vmware.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: nadav.amit@gmail.com, mgorman@suse.de, riel@redhat.com, luto@kernel.org, Minchan Kim , stable@vger.kernel.org, Nadav Amit From: Nadav Amit Setting and clearing mm->tlb_flush_pending can be performed by multiple threads, since mmap_sem may only be acquired for read in task_numa_work(). If this happens, tlb_flush_pending might be cleared while one of the threads still changes PTEs and batches TLB flushes. This can lead to the same race between migration and change_protection_range() that led to the introduction of tlb_flush_pending. The result of this race was data corruption, which means that this patch also addresses a theoretically possible data corruption. An actual data corruption was not observed, yet the race was was confirmed by adding assertion to check tlb_flush_pending is not set by two threads, adding artificial latency in change_protection_range() and using sysctl to reduce kernel.numa_balancing_scan_delay_ms. Fixes: 20841405940e ("mm: fix TLB flush race between migration, and change_protection_range") Cc: Minchan Kim Cc: Andy Lutomirski Cc: stable@vger.kernel.org Signed-off-by: Nadav Amit Acked-by: Mel Gorman Acked-by: Rik van Riel --- include/linux/mm_types.h | 31 ++++++++++++++++++++++--------- kernel/fork.c | 2 +- mm/debug.c | 2 +- mm/mprotect.c | 4 ++-- 4 files changed, 26 insertions(+), 13 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 45cdb27791a3..f5263dd0f1bc 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -493,7 +493,7 @@ struct mm_struct { * can move process memory needs to flush the TLB when moving a * PROT_NONE or PROT_NUMA mapped page. */ - bool tlb_flush_pending; + atomic_t tlb_flush_pending; #endif struct uprobes_state uprobes_state; #ifdef CONFIG_HUGETLB_PAGE @@ -528,33 +528,46 @@ static inline cpumask_t *mm_cpumask(struct mm_struct *mm) static inline bool mm_tlb_flush_pending(struct mm_struct *mm) { barrier(); - return mm->tlb_flush_pending; + return atomic_read(&mm->tlb_flush_pending) > 0; } -static inline void set_tlb_flush_pending(struct mm_struct *mm) + +static inline void init_tlb_flush_pending(struct mm_struct *mm) { - mm->tlb_flush_pending = true; + atomic_set(&mm->tlb_flush_pending, 0); +} + +static inline void inc_tlb_flush_pending(struct mm_struct *mm) +{ + atomic_inc(&mm->tlb_flush_pending); /* - * Guarantee that the tlb_flush_pending store does not leak into the + * Guarantee that the tlb_flush_pending increase does not leak into the * critical section updating the page tables */ smp_mb__before_spinlock(); } + /* Clearing is done after a TLB flush, which also provides a barrier. */ -static inline void clear_tlb_flush_pending(struct mm_struct *mm) +static inline void dec_tlb_flush_pending(struct mm_struct *mm) { barrier(); - mm->tlb_flush_pending = false; + atomic_dec(&mm->tlb_flush_pending); } #else static inline bool mm_tlb_flush_pending(struct mm_struct *mm) { return false; } -static inline void set_tlb_flush_pending(struct mm_struct *mm) + +static inline void init_tlb_flush_pending(struct mm_struct *mm) { } -static inline void clear_tlb_flush_pending(struct mm_struct *mm) + +static inline void inc_tlb_flush_pending(struct mm_struct *mm) +{ +} + +static inline void dec_tlb_flush_pending(struct mm_struct *mm) { } #endif diff --git a/kernel/fork.c b/kernel/fork.c index e53770d2bf95..840e7a7132e1 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -809,7 +809,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, mm_init_aio(mm); mm_init_owner(mm, p); mmu_notifier_mm_init(mm); - clear_tlb_flush_pending(mm); + init_tlb_flush_pending(mm); #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS mm->pmd_huge_pte = NULL; #endif diff --git a/mm/debug.c b/mm/debug.c index db1cd26d8752..d70103bb4731 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -159,7 +159,7 @@ void dump_mm(const struct mm_struct *mm) mm->numa_next_scan, mm->numa_scan_offset, mm->numa_scan_seq, #endif #if defined(CONFIG_NUMA_BALANCING) || defined(CONFIG_COMPACTION) - mm->tlb_flush_pending, + atomic_read(&mm->tlb_flush_pending), #endif mm->def_flags, &mm->def_flags ); diff --git a/mm/mprotect.c b/mm/mprotect.c index 8edd0d576254..0c413774c1e3 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -245,7 +245,7 @@ static unsigned long change_protection_range(struct vm_area_struct *vma, BUG_ON(addr >= end); pgd = pgd_offset(mm, addr); flush_cache_range(vma, addr, end); - set_tlb_flush_pending(mm); + inc_tlb_flush_pending(mm); do { next = pgd_addr_end(addr, end); if (pgd_none_or_clear_bad(pgd)) @@ -257,7 +257,7 @@ static unsigned long change_protection_range(struct vm_area_struct *vma, /* Only flush the TLB if we actually modified any entries: */ if (pages) flush_tlb_range(vma, start, end); - clear_tlb_flush_pending(mm); + dec_tlb_flush_pending(mm); return pages; } -- 2.11.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org