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Date: Fri, 7 Jul 2017 10:43:28 +0200
From: Alexander Potapenko <glider@...gle.com>
To: Dmitriy Vyukov <dvyukov@...gle.com>,
Kostya Serebryany <kcc@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH] slub: make sure struct kmem_cache_node is initialized
before publication
Hi all,
On Fri, Jul 7, 2017 at 10:34 AM, Alexander Potapenko <glider@...gle.com> wrote:
> According to KMSAN (see the report below) it's possible that
> unfreeze_partials() accesses &n->list_lock before it's being
> initialized. The initialization normally happens in
> init_kmem_cache_node() when it's called from init_kmem_cache_nodes(),
> but only after the struct kmem_cache_node is published.
> To avoid what appears to be a data race, we need to publish the struct
> after it has been initialized.
I was unsure whether we should use acquire/release primitives instead
of direct accesses to s->node[node].
If a data race here is really possible, then looks like we do.
> KMSAN (https://github.com/google/kmsan) report is as follows:
>
> ==================================================================
> BUG: KMSAN: use of uninitialized memory in
> queued_spin_lock_slowpath+0xa55/0xaf0 kernel/locking/qspinlock.c:478
> CPU: 1 PID: 5021 Comm: modprobe Not tainted 4.11.0-rc5+ #2876
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
> <IRQ>
> __dump_stack lib/dump_stack.c:16 [inline]
> dump_stack+0x172/0x1c0 lib/dump_stack.c:52
> kmsan_report+0x12a/0x180 mm/kmsan/kmsan.c:927
> __msan_warning_32+0x61/0xb0 mm/kmsan/kmsan_instr.c:469
> queued_spin_lock_slowpath+0xa55/0xaf0 kernel/locking/qspinlock.c:478
> queued_spin_lock include/asm-generic/qspinlock.h:103 [inline]
> do_raw_spin_lock include/linux/spinlock.h:148 [inline]
> __raw_spin_lock include/linux/spinlock_api_smp.h:143 [inline]
> _raw_spin_lock+0x73/0x80 kernel/locking/spinlock.c:151
> spin_lock include/linux/spinlock.h:299 [inline]
> unfreeze_partials+0x6d/0x210 mm/slub.c:2181
> put_cpu_partial mm/slub.c:2255 [inline]
> __slab_free mm/slub.c:2894 [inline]
> do_slab_free mm/slub.c:2990 [inline]
> slab_free mm/slub.c:3005 [inline]
> kmem_cache_free+0x39d/0x5b0 mm/slub.c:3020
> free_task_struct kernel/fork.c:158 [inline]
> free_task kernel/fork.c:370 [inline]
> __put_task_struct+0x7eb/0x880 kernel/fork.c:407
> put_task_struct include/linux/sched/task.h:94 [inline]
> delayed_put_task_struct+0x271/0x2b0 kernel/exit.c:181
> __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
> rcu_do_batch kernel/rcu/tree.c:2879 [inline]
> invoke_rcu_callbacks kernel/rcu/tree.c:3142 [inline]
> __rcu_process_callbacks kernel/rcu/tree.c:3109 [inline]
> rcu_process_callbacks+0x1f10/0x2b50 kernel/rcu/tree.c:3126
> __do_softirq+0x485/0x942 kernel/softirq.c:284
> invoke_softirq kernel/softirq.c:364 [inline]
> irq_exit+0x1fa/0x230 kernel/softirq.c:405
> exiting_irq+0xe/0x10 arch/x86/include/asm/apic.h:657
> smp_apic_timer_interrupt+0x5a/0x80 arch/x86/kernel/apic/apic.c:966
> apic_timer_interrupt+0x86/0x90 arch/x86/entry/entry_64.S:489
> RIP: 0010:native_restore_fl arch/x86/include/asm/irqflags.h:36 [inline]
> RIP: 0010:arch_local_irq_restore arch/x86/include/asm/irqflags.h:77
> [inline]
> RIP: 0010:__msan_poison_alloca+0xed/0x120 mm/kmsan/kmsan_instr.c:440
> RSP: 0018:ffff880023d6f7b8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
> RAX: 0000000000000246 RBX: ffff88001ebf8000 RCX: 0000000000000002
> RDX: 0000000000000001 RSI: ffff880000000000 RDI: ffffea0000b332f0
> RBP: ffff880023d6f838 R08: 0000000000000884 R09: 0000000000000004
> R10: 0000160000000000 R11: 0000000000000000 R12: ffffffff85ab5df0
> R13: ffff880023d6f885 R14: 0000000000000001 R15: ffffffff81ae424d
> </IRQ>
> page_remove_rmap+0x9d/0xd80 mm/rmap.c:1256
> zap_pte_range mm/memory.c:1237 [inline]
> zap_pmd_range mm/memory.c:1318 [inline]
> zap_pud_range mm/memory.c:1347 [inline]
> zap_p4d_range mm/memory.c:1368 [inline]
> unmap_page_range+0x28fd/0x34a0 mm/memory.c:1389
> unmap_single_vma+0x354/0x4b0 mm/memory.c:1434
> unmap_vmas+0x192/0x2a0 mm/memory.c:1464
> unmap_region+0x375/0x4c0 mm/mmap.c:2464
> do_munmap+0x1a39/0x2360 mm/mmap.c:2669
> vm_munmap mm/mmap.c:2688 [inline]
> SYSC_munmap+0x13d/0x1a0 mm/mmap.c:2698
> SyS_munmap+0x47/0x70 mm/mmap.c:2695
> entry_SYSCALL_64_fastpath+0x13/0x94
> RIP: 0033:0x7fb3c34f0d37
> RSP: 002b:00007ffd44afc268 EFLAGS: 00000206 ORIG_RAX: 000000000000000b
> RAX: ffffffffffffffda RBX: 0000563670927260 RCX: 00007fb3c34f0d37
> RDX: 0000000000000000 RSI: 0000000000001000 RDI: 00007fb3c3bd5000
> RBP: 0000000000000000 R08: 00007fb3c3bd1700 R09: 00007ffd44afc3c8
> R10: 0000000000000000 R11: 0000000000000206 R12: 00000000ffffffff
> R13: 0000563670927110 R14: 0000563670927210 R15: 00007ffd44afc4f0
> origin:
> save_stack_trace+0x37/0x40 arch/x86/kernel/stacktrace.c:59
> kmsan_save_stack_with_flags mm/kmsan/kmsan.c:302 [inline]
> kmsan_internal_poison_shadow+0xb1/0x1a0 mm/kmsan/kmsan.c:198
> kmsan_kmalloc+0x7f/0xe0 mm/kmsan/kmsan.c:337
> kmsan_post_alloc_hook+0x10/0x20 mm/kmsan/kmsan.c:350
> slab_post_alloc_hook mm/slab.h:459 [inline]
> slab_alloc_node mm/slub.c:2747 [inline]
> kmem_cache_alloc_node+0x150/0x210 mm/slub.c:2788
> init_kmem_cache_nodes mm/slub.c:3430 [inline]
> kmem_cache_open mm/slub.c:3649 [inline]
> __kmem_cache_create+0x13e/0x5f0 mm/slub.c:4290
> create_cache mm/slab_common.c:382 [inline]
> kmem_cache_create+0x186/0x220 mm/slab_common.c:467
> fork_init+0x7e/0x430 kernel/fork.c:451
> start_kernel+0x499/0x580 init/main.c:654
> x86_64_start_reservations arch/x86/kernel/head64.c:196 [inline]
> x86_64_start_kernel+0x6cc/0x700 arch/x86/kernel/head64.c:177
> verify_cpu+0x0/0xfc
> ==================================================================
>
> Signed-off-by: Alexander Potapenko <glider@...gle.com>
> ---
> mm/slub.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 1d3f9835f4ea..481e523bb30d 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3389,8 +3389,8 @@ static int init_kmem_cache_nodes(struct kmem_cache *s)
> return 0;
> }
>
> - s->node[node] = n;
> init_kmem_cache_node(n);
> + s->node[node] = n;
> }
> return 1;
> }
> --
> 2.13.2.725.g09c95d1e9-goog
>
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
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