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Message-ID: <20111213152651.GP20297@mudshark.cambridge.arm.com>
Date: Tue, 13 Dec 2011 15:26:51 +0000
From: Will Deacon <will.deacon@....com>
To: a.p.zijlstra@...llo.nl
Cc: eranian@...gle.com, mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: perf NULL pointer dereference on -rc5
Hi Peter,
Commit 10c6db11 ("perf: Fix loss of notification with multi-event") seems to
dereference a NULL event->rb in the wakeup handler during Vince Weaver's perf
tests (specifically corner_cases/overflow_requires_mmap).
This diff seems to fix the problem, but I'm not sure if it just hides something else:
diff --git a/kernel/events/core.c b/kernel/events/core.c
index d3b9df5..b466e7fc 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3558,9 +3558,13 @@ static void ring_buffer_wakeup(struct perf_event *event)
rcu_read_lock();
rb = rcu_dereference(event->rb);
+ if (!rb)
+ goto unlock;
+
list_for_each_entry_rcu(event, &rb->event_list, rb_entry) {
wake_up_all(&event->waitq);
}
+unlock:
rcu_read_unlock();
}
Log follows...
Cheers,
Will
[ 77.705045] Unable to handle kernel NULL pointer dereference at virtual address 0000004c
[ 77.732457] pgd = ef254000
[ 77.740547] [0000004c] *pgd=9f81f831
[ 77.751258] Internal error: Oops: 17 [#1] PREEMPT SMP
[ 77.766382] Modules linked in:
[ 77.775527] CPU: 0 Tainted: G W (3.2.0-rc5 #5)
[ 77.792491] PC is at perf_event_wakeup+0x18/0x88
[ 77.806315] LR is at perf_event_wakeup+0x10/0x88
[ 77.820143] pc : [<c007fbec>] lr : [<c007fbe4>] psr: 20000193
[ 77.820153] sp : ef271e80 ip : 00000007 fp : 00000118
[ 77.854552] r10: ef270000 r9 : 00000000 r8 : 00000001
[ 77.870199] r7 : ef357800 r6 : ef271e88 r5 : 00000000 r4 : ef3579e0
[ 77.889753] r3 : ef8cd6a0 r2 : 00000001 r1 : ef270000 r0 : ef357800
[ 77.909310] Flags: nzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user
[ 77.930949] Control: 10c5387d Table: 8f25404a DAC: 00000015
[ 77.948159] Process overflow_requir (pid: 3092, stack limit = 0xef2702f8)
[ 77.968495] Stack: (0xef271e80 to 0xef272000)
[ 77.981545] 1e80: 00000001 00000000 000f4071 ef3579e0 00000000 00000000 00000002 c007b30c
[ 78.006056] 1ea0: c0401da8 00000007 00000000 c0418d08 c0d3d160 c00168a8 00000002 ef3578c8
[ 78.030568] 1ec0: 00000100 ef271fb0 00000001 00000000 00008a5a 00000000 ef357000 ef82f700
[ 78.055077] 1ee0: ef821000 00000000 00000000 00000000 c03fe2b4 c01ec0a0 ef357000 c03fe080
[ 78.079588] 1f00: ef402c60 40000193 000f4240 00000000 ef1b9dc0 00000000 00000000 ef1c1640
[ 78.104098] 1f20: ef80a654 00000000 00000000 0000005c c0424198 ef80a600 00000001 c006ea94
[ 78.128608] 1f40: 00000001 00000c14 ef1b9140 ef80a600 ef80a654 ef1c1640 0000005c 00000000
[ 78.153118] 1f60: 00000004 000f4240 00000000 c006ebfc ef80a600 ef80a654 00000001 c0071500
[ 78.177628] 1f80: 0000005c c03f9c4c ef270000 c006e3e0 c03feb30 c000e9e4 00008a5a 20000030
[ 78.202138] 1fa0: f8e00100 00000003 00000001 c000deb4 00000000 00002400 00938462 00000000
[ 78.226648] 1fc0: becc46a0 00000000 000121f8 00000003 00000001 00000004 000f4240 00000000
[ 78.251159] 1fe0: 0001203c becc45c0 00008a4d 00008a5a 20000030 ffffffff 8f538c6b 2493cd43
[ 78.275697] [<c007fbec>] (perf_event_wakeup+0x18/0x88) from [<c007b30c>] (irq_work_run+0x90/0xc4)
[ 78.302314] [<c007b30c>] (irq_work_run+0x90/0xc4) from [<c00168a8>] (armv7pmu_handle_irq+0x104/0x17c)
[ 78.329970] [<c00168a8>] (armv7pmu_handle_irq+0x104/0x17c) from [<c006ea94>] (handle_irq_event_percpu+0x54/0x180)
[ 78.360741] [<c006ea94>] (handle_irq_event_percpu+0x54/0x180) from [<c006ebfc>] (handle_irq_event+0x3c/0x5c)
[ 78.390213] [<c006ebfc>] (handle_irq_event+0x3c/0x5c) from [<c0071500>] (handle_fasteoi_irq+0x9c/0x140)
[ 78.418379] [<c0071500>] (handle_fasteoi_irq+0x9c/0x140) from [<c006e3e0>] (generic_handle_irq+0x20/0x30)
[ 78.447078] [<c006e3e0>] (generic_handle_irq+0x20/0x30) from [<c000e9e4>] (handle_IRQ+0x58/0xac)
[ 78.473420] [<c000e9e4>] (handle_IRQ+0x58/0xac) from [<c000deb4>] (__irq_usr+0x34/0xa0)
[ 78.497411] Code: e24dd00c ebffcdef e59751b4 e28d6008 (e5b5304c)
[ 78.515665] ---[ end trace 1b75b31a2719ed1e ]---
[ 78.529490] Kernel panic - not syncing: Fatal exception in interrupt
[ 78.548543] [<c0013e7c>] (unwind_backtrace+0x0/0xf8) from [<c02e6cc0>] (panic+0x7c/0x1bc)
[ 78.573069] [<c02e6cc0>] (panic+0x7c/0x1bc) from [<c00118a8>] (die+0x1f4/0x1f8)
[ 78.594987] [<c00118a8>] (die+0x1f4/0x1f8) from [<c0017f60>] (__do_kernel_fault+0x74/0x84)
[ 78.619766] [<c0017f60>] (__do_kernel_fault+0x74/0x84) from [<c001810c>] (do_page_fault+0x19c/0x2f0)
[ 78.647149] [<c001810c>] (do_page_fault+0x19c/0x2f0) from [<c00083f0>] (do_DataAbort+0x34/0x9c)
[ 78.673228] [<c00083f0>] (do_DataAbort+0x34/0x9c) from [<c000dc58>] (__dabt_svc+0x38/0x60)
[ 78.697992] Exception stack(0xef271e38 to 0xef271e80)
[ 78.713119] 1e20: ef357800 ef270000
[ 78.737630] 1e40: 00000001 ef8cd6a0 ef3579e0 00000000 ef271e88 ef357800 00000001 00000000
[ 78.762141] 1e60: ef270000 00000118 00000007 ef271e80 c007fbe4 c007fbec 20000193 ffffffff
[ 78.786658] [<c000dc58>] (__dabt_svc+0x38/0x60) from [<c007fbec>] (perf_event_wakeup+0x18/0x88)
[ 78.812739] [<c007fbec>] (perf_event_wakeup+0x18/0x88) from [<c007b30c>] (irq_work_run+0x90/0xc4)
[ 78.839341] [<c007b30c>] (irq_work_run+0x90/0xc4) from [<c00168a8>] (armv7pmu_handle_irq+0x104/0x17c)
[ 78.866986] [<c00168a8>] (armv7pmu_handle_irq+0x104/0x17c) from [<c006ea94>] (handle_irq_event_percpu+0x54/0x180)
[ 78.897754] [<c006ea94>] (handle_irq_event_percpu+0x54/0x180) from [<c006ebfc>] (handle_irq_event+0x3c/0x5c)
[ 78.927221] [<c006ebfc>] (handle_irq_event+0x3c/0x5c) from [<c0071500>] (handle_fasteoi_irq+0x9c/0x140)
[ 78.955385] [<c0071500>] (handle_fasteoi_irq+0x9c/0x140) from [<c006e3e0>] (generic_handle_irq+0x20/0x30)
[ 78.984071] [<c006e3e0>] (generic_handle_irq+0x20/0x30) from [<c000e9e4>] (handle_IRQ+0x58/0xac)
[ 79.010410] [<c000e9e4>] (handle_IRQ+0x58/0xac) from [<c000deb4>] (__irq_usr+0x34/0xa0)
--
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