Hi all, While fuzzing with trinity inside a KVM tools guest running latest -next kernel I've stumbled on the following: [ 2552.313602] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 [ 2552.315878] IP: __lock_acquire (kernel/locking/lockdep.c:3070 (discriminator 1)) [ 2552.315878] PGD 465836067 PUD 465837067 PMD 0 [ 2552.315878] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 2552.315878] Dumping ftrace buffer: [ 2552.315878] (ftrace buffer empty) [ 2552.315878] Modules linked in: [ 2552.315878] CPU: 6 PID: 16173 Comm: trinity-c364 Tainted: G W 3.15.0-rc1-next-20140415-sasha-00020-gaa90d09 #398 [ 2552.315878] task: ffff88046548b000 ti: ffff88044e532000 task.ti: ffff88044e532000 [ 2552.320286] RIP: __lock_acquire (kernel/locking/lockdep.c:3070 (discriminator 1)) [ 2552.320286] RSP: 0018:ffff88044e5339c8 EFLAGS: 00010002 [ 2552.320286] RAX: 0000000000000082 RBX: ffff88046548b000 RCX: 0000000000000000 [ 2552.320286] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000018 [ 2552.320286] RBP: ffff88044e533ab8 R08: 0000000000000001 R09: 0000000000000000 [ 2552.320286] R10: ffff88046548b000 R11: 0000000000000001 R12: 0000000000000000 [ 2552.320286] R13: 0000000000000018 R14: 0000000000000000 R15: 0000000000000000 [ 2552.320286] FS: 00007fd286a9a700(0000) GS:ffff88018b000000(0000) knlGS:0000000000000000 [ 2552.320286] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 2552.320286] CR2: 0000000000000018 CR3: 0000000442c17000 CR4: 00000000000006a0 [ 2552.320286] DR0: 0000000000695000 DR1: 0000000000000000 DR2: 0000000000000000 [ 2552.320286] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 [ 2552.320286] Stack: [ 2552.320286] ffff88044e5339e8 ffffffff9f56e761 0000000000000000 ffff880315c13000 [ 2552.320286] ffff88044e533a38 ffffffff9c193f0d ffffffff9c193e34 ffff8804654e8000 [ 2552.320286] ffff8804654e8000 0000000000000001 ffff88046548b000 0000000000000007 [ 2552.320286] Call Trace: [ 2552.320286] ? _raw_spin_unlock_irq (arch/x86/include/asm/preempt.h:98 include/linux/spinlock_api_smp.h:169 kernel/locking/spinlock.c:199) [ 2552.320286] ? finish_task_switch (include/linux/tick.h:206 kernel/sched/core.c:2163) [ 2552.320286] ? finish_task_switch (arch/x86/include/asm/current.h:14 kernel/sched/sched.h:993 kernel/sched/core.c:2145) [ 2552.320286] ? retint_restore_args (arch/x86/kernel/entry_64.S:1040) [ 2552.320286] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63) [ 2552.320286] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2557 kernel/locking/lockdep.c:2599) [ 2552.320286] lock_acquire (arch/x86/include/asm/current.h:14 kernel/locking/lockdep.c:3602) [ 2552.320286] ? remove_migration_pte (mm/migrate.c:137) [ 2552.320286] ? retint_restore_args (arch/x86/kernel/entry_64.S:1040) [ 2552.320286] _raw_spin_lock (include/linux/spinlock_api_smp.h:143 kernel/locking/spinlock.c:151) [ 2552.320286] ? remove_migration_pte (mm/migrate.c:137) [ 2552.320286] remove_migration_pte (mm/migrate.c:137) [ 2552.320286] rmap_walk (mm/rmap.c:1628 mm/rmap.c:1699) [ 2552.320286] remove_migration_ptes (mm/migrate.c:224) [ 2552.320286] ? new_page_node (mm/migrate.c:107) [ 2552.320286] ? remove_migration_pte (mm/migrate.c:195) [ 2552.320286] migrate_pages (mm/migrate.c:922 mm/migrate.c:960 mm/migrate.c:1126) [ 2552.320286] ? perf_trace_mm_numa_migrate_ratelimit (mm/migrate.c:1574) [ 2552.320286] migrate_misplaced_page (mm/migrate.c:1733) [ 2552.320286] __handle_mm_fault (mm/memory.c:3762 mm/memory.c:3812 mm/memory.c:3925) [ 2552.320286] ? __const_udelay (arch/x86/lib/delay.c:126) [ 2552.320286] ? __rcu_read_unlock (kernel/rcu/update.c:97) [ 2552.320286] handle_mm_fault (mm/memory.c:3948) [ 2552.320286] __get_user_pages (mm/memory.c:1851) [ 2552.320286] ? preempt_count_sub (kernel/sched/core.c:2527) [ 2552.320286] __mlock_vma_pages_range (mm/mlock.c:255) [ 2552.320286] __mm_populate (mm/mlock.c:711) [ 2552.320286] SyS_mlockall (include/linux/mm.h:1799 mm/mlock.c:817 mm/mlock.c:791) [ 2552.320286] tracesys (arch/x86/kernel/entry_64.S:749) [ 2552.320286] Code: 85 2d 1e 00 00 48 c7 c1 d7 68 6c a0 48 c7 c2 47 11 6c a0 31 c0 be fa 0b 00 00 48 c7 c7 91 68 6c a0 e8 1c 6d f9 ff e9 07 1e 00 00 <49> 81 7d 00 80 31 76 a2 b8 00 00 00 00 44 0f 44 c0 eb 07 0f 1f [ 2552.320286] RIP __lock_acquire (kernel/locking/lockdep.c:3070 (discriminator 1)) [ 2552.320286] RSP <ffff88044e5339c8> [ 2552.320286] CR2: 0000000000000018 Thanks, Sasha -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>