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Date: Wed, 17 Sep 2014 17:30:07 -0400 From: Sasha Levin <sasha.levin@...cle.com> To: Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org> CC: Dave Jones <davej@...hat.com>, LKML <linux-kernel@...r.kernel.org> Subject: sched: NULL ptr deref in update_blocked_averages Hi all, While fuzzing with trinity inside a KVM tools guest running the latest -next kernel, I've stumbled on the following spew: [ 688.177091] BUG: unable to handle kernel NULL pointer dereference at 00000000000000e0 [ 688.184049] IP: update_blocked_averages (kernel/sched/fair.c:5512 (discriminator 17) kernel/sched/fair.c:5557 (discriminator 17)) [ 688.186981] PGD 66fe03067 PUD 66f550067 PMD 0 [ 688.186981] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 688.186981] Dumping ftrace buffer: [ 688.186981] (ftrace buffer empty) [ 688.186981] Modules linked in: [ 688.186981] CPU: 2 PID: 14377 Comm: trinity-c269 Tainted: G W 3.17.0-rc5-next-20140917-sasha-00041-gd01267b #1198 [ 688.186981] task: ffff88068c02b000 ti: ffff8806478ec000 task.ti: ffff8806478ec000 [ 688.186981] RIP: update_blocked_averages (kernel/sched/fair.c:5512 (discriminator 17) kernel/sched/fair.c:5557 (discriminator 17)) [ 688.186981] RSP: 0018:ffff880111c03dc8 EFLAGS: 00010006 [ 688.186981] RAX: 0000000000000000 RBX: ffff880111de2a00 RCX: 0000000000000000 [ 688.186981] RDX: 0000000000000002 RSI: ffffffffa408a480 RDI: 0000000000000082 [ 688.186981] RBP: ffff880111c03e18 R08: 0000000000000000 R09: 0000000000000000 [ 688.186981] R10: ffff880102a8dbe0 R11: ffff880111de2ac8 R12: ffff8800a1b23b10 [ 688.186981] R13: ffff8800a1b23bd0 R14: 0000000000000000 R15: ffff880111de3330 [ 688.186981] FS: 00007ff7df150700(0000) GS:ffff880111c00000(0000) knlGS:0000000000000000 [ 688.186981] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 688.186981] CR2: 00000000000000e0 CR3: 000000066fe02000 CR4: 00000000000006a0 [ 688.186981] Stack: [ 688.186981] 0000001200000003 0000000000000296 0000000000000002 ffff8800a1b23bd0 [ 688.186981] ffff880111c03e28 00000001000097a2 0000000000000007 0000000000000007 [ 688.186981] 0000000000000001 0000000000000001 ffff880111c03e98 ffffffff9f1abc8b [ 688.186981] Call Trace: [ 688.186981] <IRQ> [ 688.186981] rebalance_domains (kernel/sched/fair.c:7240) [ 688.186981] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2559 kernel/locking/lockdep.c:2601) [ 688.186981] run_rebalance_domains (kernel/sched/fair.c:7449) [ 688.186981] ? __lock_is_held (kernel/locking/lockdep.c:3518) [ 688.186981] __do_softirq (kernel/softirq.c:269 include/linux/jump_label.h:114 include/trace/events/irq.h:126 kernel/softirq.c:270) [ 688.186981] ? irq_exit (include/linux/vtime.h:82 include/linux/vtime.h:121 kernel/softirq.c:384) [ 688.186981] irq_exit (kernel/softirq.c:346 kernel/softirq.c:387) [ 688.186981] smp_trace_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:969) [ 688.232227] FAULT_INJECTION: forcing a failure [ 688.186981] trace_apic_timer_interrupt (arch/x86/kernel/entry_64.S:999) [ 688.186981] <EOI> [ 688.186981] ? _raw_spin_unlock_irqrestore (./arch/x86/include/asm/paravirt.h:809 include/linux/spinlock_api_smp.h:160 kernel/locking/spinlock.c:191) [ 688.186981] p9_virtio_request (net/9p/trans_virtio.c:312) [ 688.186981] p9_client_rpc (net/9p/client.c:748) [ 688.186981] ? v9fs_file_fsync_dotl (fs/9p/vfs_file.c:568) [ 688.186981] ? preempt_count_sub (kernel/sched/core.c:2634) [ 688.186981] p9_client_fsync (net/9p/client.c:1433) [ 688.186981] v9fs_file_fsync_dotl (fs/9p/vfs_file.c:573) [ 688.186981] do_fsync (include/linux/file.h:38 fs/sync.c:207) [ 688.186981] SyS_fsync (fs/sync.c:212) [ 688.186981] tracesys_phase2 (arch/x86/kernel/entry_64.S:529) [ 688.186981] Code: 30 09 00 00 4d 8d a5 40 ff ff ff 4d 39 ef 0f 84 95 02 00 00 0f 1f 84 00 00 00 00 00 49 8b 84 24 d0 00 00 00 48 63 93 f8 09 00 00 <48> 8b 88 e0 00 00 00 4c 8b 2c d1 66 66 66 66 90 48 8b 80 d8 00 All code ======== 0: 30 09 xor %cl,(%rcx) 2: 00 00 add %al,(%rax) 4: 4d 8d a5 40 ff ff ff lea -0xc0(%r13),%r12 b: 4d 39 ef cmp %r13,%r15 e: 0f 84 95 02 00 00 je 0x2a9 14: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1) 1b: 00 1c: 49 8b 84 24 d0 00 00 mov 0xd0(%r12),%rax 23: 00 24: 48 63 93 f8 09 00 00 movslq 0x9f8(%rbx),%rdx 2b:* 48 8b 88 e0 00 00 00 mov 0xe0(%rax),%rcx <-- trapping instruction 32: 4c 8b 2c d1 mov (%rcx,%rdx,8),%r13 36: 66 66 66 66 90 data32 data32 data32 xchg %ax,%ax 3b: 48 rex.W 3c: 8b .byte 0x8b 3d: 80 d8 00 sbb $0x0,%al ... Code starting with the faulting instruction =========================================== 0: 48 8b 88 e0 00 00 00 mov 0xe0(%rax),%rcx 7: 4c 8b 2c d1 mov (%rcx,%rdx,8),%r13 b: 66 66 66 66 90 data32 data32 data32 xchg %ax,%ax 10: 48 rex.W 11: 8b .byte 0x8b 12: 80 d8 00 sbb $0x0,%al ... [ 688.186981] RIP update_blocked_averages (kernel/sched/fair.c:5512 (discriminator 17) kernel/sched/fair.c:5557 (discriminator 17)) [ 688.186981] RSP <ffff880111c03dc8> [ 688.186981] CR2: 00000000000000e0 Thanks, Sasha -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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