Hi all, On Fri, Jul 7, 2017 at 10:34 AM, Alexander Potapenko <gli...@google.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 <gli...@google.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 >
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