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Date: Sat, 30 Nov 2013 16:28:41 +0100
From: Kristian Nielsen <knielsen@...elsen-hq.org>
To: Benjamin LaHaise <bcrl@...ck.org>
Cc: Kent Overstreet <kmo@...erainc.com>, Dave Jones <davej@...hat.com>,
Linux Kernel <linux-kernel@...r.kernel.org>,
Sasha Levin <sasha.levin@...cle.com>
Subject: Re: GPF in aio_migratepage
Benjamin LaHaise <bcrl@...ck.org> writes:
> For Dave: what line is this bug on? Is it the dereference of ctx when
> doing spin_lock_irqsave(&ctx->completion_lock, flags); or is the
> ctx->ring_pages[idx] = new; ? From the 64 bit splat, I'm thinking the
> former, which is quite strange given that the clearing of
> mapping->private_data is protected by mapping->private_lock. If it's
> the latter, we might well need to check if ctx->ring_pages is NULL during
> setup.
I think I got the same BUG (at least it looks very similar, full details
below).
The bug is on this line:
ctx->ring_pages[idx] = new;
Disassembly:
af7: 48 89 2c d1 mov %rbp,(%rcx,%rdx,8)
ctx->ring_pages is 0xffffffffffffffff (this is x86_64). idx is 13.
RCX: ffffffffffffffff RDX: 000000000000000d
BUG: unable to handle kernel NULL pointer dereference at 0000000000000067
So we are de-referencing a pointer that is (page **)-1, causing the crash.
If you look closer at the 32-bit dump that Dave gave, you can see that it is
similar:
7a2: 89 34 82 mov %esi,(%edx,%eax,4)
RAX: 6b6b6b6b6b6b6b6b RDX: 0000000000000000
Though in this case ctx->ring_pages seems to be NULL and idx=old->index seems
to be 6b6b6b6b6b6b6b6b, so not completely the same (or maybe I read his dump
incorrectly).
This is 3.13-rc1. Unfortunately, I do not have a way to reproduce (so far I
only saw it this once). But I can see if it turns up again, or should I
install -rc2 and see if it goes away?
I was not doing anything special at the time, normal desktop load (I was using
the evince pdf viewer).
Let me know if there is anything else I can do to help track this down?
- Kristian.
Full details:
I put my .config here:
http://knielsen-hq.org/config-3.13-rc1-gpf-in-aio-migratepage.txt
BUG output:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000067
IP: [<ffffffff8113d73f>] aio_migratepage+0xb3/0xe4
PGD 0
Oops: 0002 [#1] SMP
Modules linked in: tun parport_pc ppdev lp parport bnep rfcomm bluetooth cpufreq_userspace cpufreq_stats cpufreq_powersave cpufreq_conservative binfmt_misc uinput fuse nfsd auth_rpcgss oid_registry nfs_acl nfs lockd fscache sunrpc ext3 jbd loop snd_hda_codec_hdmi hid_generic usbhid hid joydev ums_realtek usb_storage snd_hda_codec_realtek iTCO_wdt iTCO_vendor_support arc4 brcmsmac cordic brcmutil b43 mac80211 cfg80211 ssb mmc_core rfkill rng_core pcmcia pcmcia_core nouveau mxm_wmi wmi x86_pkg_temp_thermal coretemp snd_hda_intel kvm_intel snd_hda_codec snd_hwdep snd_pcm_oss kvm snd_mixer_oss snd_seq_midi snd_seq_midi_event snd_pcm crc32c_intel snd_rawmidi snd_page_alloc snd_seq ghash_clmulni_intel snd_timer snd_seq_device lpc_ich aesni_intel mfd_core ttm battery aes_x86_64 ablk_helper drm_kms_helper cryptd lrw gf128mul drm glue_helper psmouse snd pcspkr serio_raw i2c_i801 evdev ehci_pci soundcore ehci_hcd bcma ac acpi_cpufreq video button processor ext4 crc16 jbd2 mbc
r_mod cdrom crc_t10dif crct10dif_common microcode ahci libahci xhci_hcd libata usbcore scsi_mod usb_common fan thermal thermal_sys r8169 mii
CPU: 2 PID: 15596 Comm: evince Not tainted 3.13.0-rc1-kn #1
Hardware name: Compal PBL2021/Base Board Product Name, BIOS 2.40 08/26/2011
task: ffff88010322f7c0 ti: ffff880102b48000 task.ti: ffff880102b48000
RIP: 0010:[<ffffffff8113d73f>] [<ffffffff8113d73f>] aio_migratepage+0xb3/0xe4
RSP: 0018:ffff880102b49798 EFLAGS: 00010213
RAX: 0000000000000286 RBX: ffffea00038f1640 RCX: ffffffffffffffff
RDX: 000000000000000d RSI: ffffea00038f1640 RDI: ffffea00038f1640
RBP: ffffea0007b6a800 R08: 0000000000000000 R09: 000000000000000d
R10: 0000000000000038 R11: ffffea0007b6a800 R12: ffff880144a30d00
R13: 0000000000000000 R14: ffff88014ba5b1f8 R15: ffff880144a30ec4
FS: 00007f68ecfe8960(0000) GS:ffff88024f480000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000067 CR3: 0000000051ee8000 CR4: 00000000000407e0
Stack:
000000000000000e 0000000000000286 ffff88024f7f6d80 ffffea00038f1640
ffffea0007b6a800 0000000000000000 ffff88014ba5b170 0000000000000001
0000000000000001 ffffffff810ffc68 ffff88014ba5b1a8 0000000000000000
Call Trace:
[<ffffffff810ffc68>] ? move_to_new_page+0x84/0x1ab
[<ffffffff810cbcbd>] ? get_page+0x9/0x25
[<ffffffff8110019e>] ? migrate_pages+0x330/0x524
[<ffffffff810dac77>] ? isolate_freepages_block+0x237/0x237
[<ffffffff810db651>] ? compact_zone+0x13a/0x301
[<ffffffff810dba3e>] ? compact_zone_order+0x94/0xa7
[<ffffffff810dbae9>] ? try_to_compact_pages+0x98/0xec
[<ffffffff8138ef42>] ? __alloc_pages_direct_compact+0xa9/0x19a
[<ffffffff810c8567>] ? __alloc_pages_nodemask+0x46f/0x7f3
[<ffffffff812cf2bc>] ? __kmalloc_reserve.isra.42+0x2a/0x6d
[<ffffffff810f64df>] ? alloc_pages_current+0xac/0xc6
[<ffffffff812cbd47>] ? sock_alloc_send_pskb+0x1fc/0x345
[<ffffffff812d2625>] ? memcpy_fromiovecend+0x48/0x6f
[<ffffffff812d2ac5>] ? skb_copy_datagram_from_iovec+0x128/0x1f2
[<ffffffff812ca529>] ? sk_wake_async+0x19/0x3c
[<ffffffff8134c605>] ? unix_stream_sendmsg+0x12e/0x2e9
[<ffffffff812c8001>] ? sock_aio_write+0xc0/0xd5
[<ffffffff81115581>] ? set_restore_sigmask+0x2d/0x2d
[<ffffffff81106da4>] ? do_sync_readv_writev+0x48/0x6b
[<ffffffff812c7f41>] ? sock_alloc_file+0x119/0x119
[<ffffffff81107e9c>] ? do_readv_writev+0xb4/0x121
[<ffffffff812c7f41>] ? sock_alloc_file+0x119/0x119
[<ffffffff810015d7>] ? __switch_to+0x1b1/0x3de
[<ffffffff8111c1ce>] ? fget_light+0x6b/0x7c
[<ffffffff81106d10>] ? fdget+0xe/0x17
[<ffffffff8110807d>] ? SyS_writev+0x51/0xaa
[<ffffffff813997e2>] ? system_call_fastpath+0x16/0x1b
Code: 48 89 de 48 89 ef 48 89 44 24 08 e8 03 22 fc ff 48 8b 53 10 49 3b 94 24 a0 00 00 00 48 8b 44 24 08 73 0c 49 8b 8c 24 98 00 00 00 <48> 89 2c d1 48 89 c6 4c 89 ff e8 74 6e 25 00 eb 06 41 bd f0 ff
RIP [<ffffffff8113d73f>] aio_migratepage+0xb3/0xe4
RSP <ffff880102b49798>
CR2: 0000000000000067
---[ end trace be5b4877a98efec5 ]---
------------[ cut here ]------------
After this I got lots of stuff like
WARNING: CPU: 4 PID: 15642 at kernel/watchdog.c:245 watchdog_overflow_callback+0x80/0xa3()
Watchdog detected hard LOCKUP on cpu 4
BUG: soft lockup - CPU#3 stuck for 22s! [EvJobScheduler:15653]
But I assume that is just due to crashing with two spinlocks held.
Disassembly of aio_migratepage():
0000000000000a44 <aio_migratepage>:
a44: 41 57 push %r15
a46: 41 56 push %r14
a48: 41 55 push %r13
a4a: 41 54 push %r12
a4c: 55 push %rbp
a4d: 53 push %rbx
a4e: 48 89 d3 mov %rdx,%rbx
a51: 48 83 ec 18 sub $0x18,%rsp
a55: 48 8b 02 mov (%rdx),%rax
a58: f6 c4 20 test $0x20,%ah
a5b: 74 02 je a5f <aio_migratepage+0x1b>
a5d: 0f 0b ud2
a5f: 49 89 fc mov %rdi,%r12
a62: 48 89 d7 mov %rdx,%rdi
a65: 48 89 f5 mov %rsi,%rbp
a68: 89 4c 24 08 mov %ecx,0x8(%rsp)
a6c: e8 00 00 00 00 callq a71 <aio_migratepage+0x2d>
a71: 44 8b 44 24 08 mov 0x8(%rsp),%r8d
a76: 31 c9 xor %ecx,%ecx
a78: 48 89 da mov %rbx,%rdx
a7b: 48 89 ee mov %rbp,%rsi
a7e: 4c 89 e7 mov %r12,%rdi
a81: e8 00 00 00 00 callq a86 <aio_migratepage+0x42>
a86: 85 c0 test %eax,%eax
a88: 41 89 c5 mov %eax,%r13d
a8b: 74 0a je a97 <aio_migratepage+0x53>
a8d: 48 89 df mov %rbx,%rdi
a90: e8 92 ff ff ff callq a27 <get_page>
a95: eb 7f jmp b16 <aio_migratepage+0xd2>
a97: 4d 8d b4 24 88 00 00 lea 0x88(%r12),%r14
a9e: 00
a9f: 48 89 ef mov %rbp,%rdi
aa2: e8 80 ff ff ff callq a27 <get_page>
aa7: 4c 89 f7 mov %r14,%rdi
aaa: e8 00 00 00 00 callq aaf <aio_migratepage+0x6b>
aaf: 4d 8b a4 24 a0 00 00 mov 0xa0(%r12),%r12
ab6: 00
ab7: 4d 85 e4 test %r12,%r12
aba: 74 4c je b08 <aio_migratepage+0xc4>
abc: 4d 8d bc 24 c4 01 00 lea 0x1c4(%r12),%r15
ac3: 00
ac4: 4c 89 ff mov %r15,%rdi
ac7: e8 00 00 00 00 callq acc <aio_migratepage+0x88>
acc: 48 89 de mov %rbx,%rsi
acf: 48 89 ef mov %rbp,%rdi
ad2: 48 89 44 24 08 mov %rax,0x8(%rsp)
ad7: e8 00 00 00 00 callq adc <aio_migratepage+0x98>
adc: 48 8b 53 10 mov 0x10(%rbx),%rdx
ae0: 49 3b 94 24 a0 00 00 cmp 0xa0(%r12),%rdx
ae7: 00
ae8: 48 8b 44 24 08 mov 0x8(%rsp),%rax
aed: 73 0c jae afb <aio_migratepage+0xb7>
aef: 49 8b 8c 24 98 00 00 mov 0x98(%r12),%rcx
af6: 00
# We get the crash on this next instruction, %rcx is 0xffffffffffffffff
af7: 48 89 2c d1 mov %rbp,(%rcx,%rdx,8)
afb: 48 89 c6 mov %rax,%rsi
afe: 4c 89 ff mov %r15,%rdi
b01: e8 00 00 00 00 callq b06 <aio_migratepage+0xc2>
b06: eb 06 jmp b0e <aio_migratepage+0xca>
b08: 41 bd f0 ff ff ff mov $0xfffffff0,%r13d
b0e: 4c 89 f7 mov %r14,%rdi
b11: e8 b7 fa ff ff callq 5cd <spin_unlock>
b16: 48 83 c4 18 add $0x18,%rsp
b1a: 44 89 e8 mov %r13d,%eax
b1d: 5b pop %rbx
b1e: 5d pop %rbp
b1f: 41 5c pop %r12
b21: 41 5d pop %r13
b23: 41 5e pop %r14
b25: 41 5f pop %r15
b27: c3 retq
--
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