Re: net-next boot error

[Steven Rostedt]

[ Added Thomas Gleixner ]


On Thu, 26 Jul 2018 11:34:39 +0200
Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:

> On Thu, Jul 26, 2018 at 11:29 AM, syzbot
> <syzbot+604f8271211546f5b3c7@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    dc66fe43b7eb rds: send: Fix dead code in rds_sendmsg
> > git tree:       net-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=127874c8400000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=f34ce142a9f5f0e8
> > dashboard link: https://syzkaller.appspot.com/bug?extid=604f8271211546f5b3c7
> > compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+604f8271211546f5b3c7@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > possible deadlock in static_key_slow_incsd 0:0:1:0: [sda] Attached SCSI disk
> > MACsec IEEE 802.1AE
> > tun: Universal TUN/TAP device driver, 1.6
> >
> > ============================================
> > WARNING: possible recursive locking detected  
> 
> +Tetsuo, perhaps this boot lockdep problem then disables lockdep for
> actual testing. I think lockdep should respect panic_on_warn.
> 
> 
> > 4.18.0-rc6+ #141 Not tainted
> > --------------------------------------------
> > swapper/0/1 is trying to acquire lock:
> > (____ptrval____) (cpu_hotplug_lock.rw_sem){++++}, at:
> > static_key_slow_inc+0x12/0x30 kernel/jump_label.c:124
> >
> > but task is already holding lock:
> > (____ptrval____) (cpu_hotplug_lock.rw_sem){++++}, at: get_online_cpus
> > include/linux/cpu.h:126 [inline]
> > (____ptrval____) (cpu_hotplug_lock.rw_sem){++++}, at: init_vqs+0xe1a/0x1520
> > drivers/net/virtio_net.c:2777

Here init_vqs() does:

	get_online_cpus();
	virtnet_set_affinity(vi);
	put_online_cpus();

Which disables cpu hotplug and calls virtnet_set_affinity()

Note, get_online_cpus() is no longer recursive.

> >
> > other info that might help us debug this:
> >  Possible unsafe locking scenario:
> >
> >        CPU0
> >        ----
> >   lock(cpu_hotplug_lock.rw_sem);
> >   lock(cpu_hotplug_lock.rw_sem);
> >
> >  *** DEADLOCK ***
> >
> >  May be due to missing lock nesting notation
> >
> > 3 locks held by swapper/0/1:
> >  #0: (____ptrval____) (&dev->mutex){....}, at: device_lock
> > include/linux/device.h:1134 [inline]
> >  #0: (____ptrval____) (&dev->mutex){....}, at: __driver_attach+0x15f/0x2f0
> > drivers/base/dd.c:820
> >  #1: (____ptrval____) (cpu_hotplug_lock.rw_sem){++++}, at: get_online_cpus
> > include/linux/cpu.h:126 [inline]
> >  #1: (____ptrval____) (cpu_hotplug_lock.rw_sem){++++}, at:
> > init_vqs+0xe1a/0x1520 drivers/net/virtio_net.c:2777
> >  #2: (____ptrval____) (xps_map_mutex){+.+.}, at:
> > __netif_set_xps_queue+0x243/0x23f0 net/core/dev.c:2278
> >
> > stack backtrace:
> > CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.18.0-rc6+ #141
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:77 [inline]
> >  dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
> >  print_deadlock_bug kernel/locking/lockdep.c:1765 [inline]
> >  check_deadlock kernel/locking/lockdep.c:1809 [inline]
> >  validate_chain kernel/locking/lockdep.c:2405 [inline]
> >  __lock_acquire.cold.65+0x1fb/0x486 kernel/locking/lockdep.c:3435
> >  lock_acquire+0x1e4/0x540 kernel/locking/lockdep.c:3924
> >  percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline]
> >  percpu_down_read include/linux/percpu-rwsem.h:59 [inline]
> >  cpus_read_lock+0x43/0xa0 kernel/cpu.c:289
> >  static_key_slow_inc+0x12/0x30 kernel/jump_label.c:124
> >  __netif_set_xps_queue+0xaac/0x23f0 net/core/dev.c:2320


__netif_set_xps_queue() calls static_key_slow_inc() which will also do
a get_online_cpus() which will trigger this bug.

There's a static_key_slow_inc_cpuslocked() version that should be used
when get_online_cpus() is already taken, but I see
__netif_set_xps_queue() is called from several places, and I doubt it
is always called with get_online_cpus() held. Thus just using the
cpuslocked() version is probably not sufficient of a fix.

I don't know the code enough to offer other suggestions.

-- Steve


> >  netif_set_xps_queue+0x26/0x30 net/core/dev.c:2455
> >  virtnet_set_affinity+0x2ba/0x4b0 drivers/net/virtio_net.c:1944
> >  init_vqs+0xe22/0x1520 drivers/net/virtio_net.c:2778
> >  virtnet_probe+0x1092/0x2260 drivers/net/virtio_net.c:3016
> >  virtio_dev_probe+0x592/0x942 drivers/virtio/virtio.c:245
> >  really_probe drivers/base/dd.c:446 [inline]
> >  driver_probe_device+0x6ad/0x970 drivers/base/dd.c:588
> >  __driver_attach+0x28b/0x2f0 drivers/base/dd.c:822
> >  bus_for_each_dev+0x15d/0x1f0 drivers/base/bus.c:311
> >  driver_attach+0x3d/0x50 drivers/base/dd.c:841
> >  bus_add_driver+0x4b2/0x600 drivers/base/bus.c:667
> >  driver_register+0x1c8/0x320 drivers/base/driver.c:170
> >  register_virtio_driver+0x79/0xd0 drivers/virtio/virtio.c:296
> >  virtio_net_driver_init+0x8d/0xc9 drivers/net/virtio_net.c:3209
> >  do_one_initcall+0x127/0x913 init/main.c:884
> >  do_initcall_level init/main.c:952 [inline]
> >  do_initcalls init/main.c:960 [inline]
> >  do_basic_setup init/main.c:978 [inline]
> >  kernel_init_freeable+0x49b/0x58e init/main.c:1135
> >  kernel_init+0x11/0x1b3 init/main.c:1061
> >  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
> > vcan: Virtual CAN interface driver
> > vxcan: Virtual CAN Tunnel driver
> > slcan: serial line CAN interface driver
> > slcan: 10 dynamic interface channels.
> > CAN device driver interface
> > enic: Cisco VIC Ethernet NIC Driver, ver 2.3.0.53
> > e100: Intel(R) PRO/100 Network Driver, 3.5.24-k2-NAPI
> > e100: Copyright(c) 1999-2006 Intel Corporation
> > e1000: Intel(R) PRO/1000 Network Driver - version 7.3.21-k8-NAPI
> > e1000: Copyright (c) 1999-2006 Intel Corporation.
> > e1000e: Intel(R) PRO/1000 Network Driver - 3.2.6-k
> > e1000e: Copyright(c) 1999 - 2015 Intel Corporation.
> > sky2: driver version 1.30
> > PPP generic driver version 2.4.2
> > PPP BSD Compression module registered
> > PPP Deflate Compression module registered
> > PPP MPPE Compression module registered
> > NET: Registered protocol family 24
> > PPTP driver version 0.8.5
> > mac80211_hwsim: initializing netlink
> > ieee80211 phy0: Selected rate control algorithm 'minstrel_ht'
> > ieee80211 phy1: Selected rate control algorithm 'minstrel_ht'
> > usbcore: registered new interface driver asix
> > usbcore: registered new interface driver ax88179_178a
> > usbcore: registered new interface driver cdc_ether
> > usbcore: registered new interface driver net1080
> > usbcore: registered new interface driver cdc_subset
> > usbcore: registered new interface driver zaurus
> > usbcore: registered new interface driver cdc_ncm
> > aoe: AoE v85 initialised.
> > ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
> > ehci-pci: EHCI PCI platform driver
> > ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
> > ohci-pci: OHCI PCI platform driver
> > uhci_hcd: USB Universal Host Controller Interface driver
> > usbcore: registered new interface driver usblp
> > usbcore: registered new interface driver usb-storage
> > i8042: PNP: PS/2 Controller [PNP0303:KBD,PNP0f13:MOU] at 0x60,0x64 irq 1,12
> > i8042: Warning: Keylock active
> > serio: i8042 KBD port at 0x60,0x64 irq 1
> > serio: i8042 AUX port at 0x60,0x64 irq 12
> > mousedev: PS/2 mouse device common for all mice
> > rtc_cmos 00:00: RTC can wake from S4
> > rtc_cmos 00:00: registered as rtc0
> > rtc_cmos 00:00: alarms up to one day, 114 bytes nvram
> > i2c /dev entries driver
> > piix4_smbus 0000:00:01.3: SMBus base address uninitialized - upgrade BIOS or
> > use force_addr=0xaddr
> > i2c-parport-light: adapter type unspecified
> > usbcore: registered new interface driver RobotFuzz Open Source InterFace,
> > OSIF
> > usbcore: registered new interface driver i2c-tiny-usb
> > device-mapper: ioctl: 4.39.0-ioctl (2018-04-03) initialised:
> > dm-devel@xxxxxxxxxx
> > device-mapper: raid: Loading target version 1.13.2
> > usbcore: registered new interface driver btusb
> > usnic_verbs: Cisco VIC (USNIC) Verbs Driver v1.0.3 (December 19, 2013)
> > usnic_verbs:usnic_uiom_init:585:
> > IOMMU required but not present or enabled.  USNIC QPs will not function w/o
> > enabling IOMMU
> > usnic_verbs:usnic_ib_init:649:
> > Unable to initalize umem with err -1
> > iscsi: registered transport (iser)
> > OPA Virtual Network Driver - v1.0
> > hidraw: raw HID events driver (C) Jiri Kosina
> > usbcore: registered new interface driver usbhid
> > usbhid: USB HID core driver
> > NET: Registered protocol family 40
> > ashmem: initialized
> > NET: Registered protocol family 26
> > Mirror/redirect action on
> > Simple TC action Loaded
> > netem: version 1.3
> > u32 classifier
> >     Actions configured
> > nf_conntrack_irc: failed to register helpers
> > nf_conntrack_sane: failed to register helpers
> > nf_conntrack_sip: failed to register helpers
> > xt_time: kernel timezone is -0000
> > IPVS: Registered protocols (TCP, UDP, SCTP, AH, ESP)
> > IPVS: Connection hash table configured (size=4096, memory=64Kbytes)
> > IPVS: ipvs loaded.
> > IPVS: [rr] scheduler registered.
> > IPVS: [wrr] scheduler registered.
> > IPVS: [lc] scheduler registered.
> > IPVS: [wlc] scheduler registered.
> > IPVS: [fo] scheduler registered.
> > IPVS: [ovf] scheduler registered.
> > IPVS: [lblc] scheduler registered.
> > IPVS: [lblcr] scheduler registered.
> > IPVS: [dh] scheduler registered.
> > IPVS: [sh] scheduler registered.
> > IPVS: [mh] scheduler registered.
> > IPVS: [sed] scheduler registered.
> > IPVS: [nq] scheduler registered.
> > IPVS: ftp: loaded support on port[0] = 21
> > IPVS: [sip] pe registered.
> > ipip: IPv4 and MPLS over IPv4 tunneling driver
> > gre: GRE over IPv4 demultiplexor driver
> > ip_gre: GRE over IPv4 tunneling driver
> > IPv4 over IPsec tunneling driver
> > ipt_CLUSTERIP: ClusterIP Version 0.8 loaded successfully
> > Initializing XFRM netlink socket
> > NET: Registered protocol family 10
> > Segment Routing with IPv6
> > mip6: Mobile IPv6
> > sit: IPv6, IPv4 and MPLS over IPv4 tunneling driver
> > ip6_gre: GRE over IPv6 tunneling driver
> > bpfilter: Loaded bpfilter_umh pid 2080
> > NET: Registered protocol family 15
> > Bridge firewalling registered
> > can: controller area network core (rev 20170425 abi 9)
> > NET: Registered protocol family 29
> > can: raw protocol (rev 20170425)
> > can: broadcast manager protocol (rev 20170425 t)
> > can: netlink gateway (rev 20170425) max_hops=1
> > Bluetooth: RFCOMM TTY layer initialized
> > Bluetooth: RFCOMM socket layer initialized
> > Bluetooth: RFCOMM ver 1.11
> > Bluetooth: BNEP (Ethernet Emulation) ver 1.3
> > Bluetooth: BNEP filters: protocol multicast
> > Bluetooth: BNEP socket layer initialized
> > Bluetooth: HIDP (Human Interface Emulation) ver 1.2
> > Bluetooth: HIDP socket layer initialized
> > RPC: Registered rdma transport module.
> > RPC: Registered rdma backchannel transport module.
> > NET: Registered protocol family 41
> > lec:lane_module_init: lec.c: initialized
> > mpoa:atm_mpoa_init: mpc.c: initialized
> > l2tp_core: L2TP core driver, V2.0
> > l2tp_ppp: PPPoL2TP kernel driver, V2.0
> > 8021q: 802.1Q VLAN Support v1.8
> > input: AT Translated Set 2 keyboard as
> > /devices/platform/i8042/serio0/input/input2
> > DCCP: Activated CCID 2 (TCP-like)
> > DCCP: Activated CCID 3 (TCP-Friendly Rate Control)
> > sctp: Hash tables configured (bind 64/64)
> > tipc: Activated (version 2.0.0)
> > NET: Registered protocol family 30
> > tipc: Started in single node mode
> > NET: Registered protocol family 43
> > 9pnet: Installing 9P2000 support
> > NET: Registered protocol family 36
> > Key type dns_resolver registered
> > Key type ceph registered
> > libceph: loaded (mon/osd proto 15/24)
> > openvswitch: Open vSwitch switching datapath
> > mpls_gso: MPLS GSO support
> > start plist test
> > end plist test
> > AVX2 version of gcm_enc/dec engaged.
> > AES CTR mode by8 optimization enabled
> > sched_clock: Marking stable (4559438359, 0)->(6126385605, -1566947246)
> > registered taskstats version 1
> > Loading compiled-in X.509 certificates
> > zswap: default zpool zbud not available
> > zswap: pool creation failed
> > Btrfs loaded, crc32c=crc32c-intel
> > Key type big_key registered
> > Key type encrypted registered
> >   Magic number: 10:317:168
> > console [netcon0] enabled
> > netconsole: network logging started
> > gtp: GTP module loaded (pdp ctx size 104 bytes)
> > rdma_rxe: loaded
> > cfg80211: Loading compiled-in X.509 certificates for regulatory database
> > cfg80211: Loaded X.509 cert 'sforshee: 00b28ddf47aef9cea7'
> > platform regulatory.0: Direct firmware load for regulatory.db failed with
> > error -2
> > cfg80211: failed to load regulatory.db
> > ALSA device list:
> >   #0: Dummy 1
> >   #1: Loopback 1
> >   #2: Virtual MIDI Card 1
> > input: ImExPS/2 Generic Explorer Mouse as
> > /devices/platform/i8042/serio1/input/input4
> > md: Waiting for all devices to be available before autodetect
> > md: If you don't use raid, use raid=noautodetect
> > md: Autodetecting RAID arrays.
> > md: autorun ...
> > md: ... autorun DONE.
> > EXT4-fs (sda1): mounted filesystem with ordered data mode. Opts: (null)
> > VFS: Mounted root (ext4 filesystem) readonly on device 8:1.
> > devtmpfs: mounted
> > Freeing unused kernel memory: 3900K
> > Kernel memory protection disabled.
> > SELinux:  Disabled at runtime.
> > SELinux:  Unregistering netfilter hooks
> > audit: type=1404 audit(1532588961.277:2): enforcing=0 old_enforcing=0
> > auid=4294967295 ses=4294967295 enabled=0 old-enabled=1 lsm=selinux res=1
> > stty (2166) used greatest stack depth: 19664 bytes left
> > EXT4-fs (sda1): re-mounted. Opts: (null)
> > logsave (3615) used greatest stack depth: 17632 bytes left
> > random: dd: uninitialized urandom read (512 bytes read)
> > ==================================================================
> > BUG: KASAN: slab-out-of-bounds in virtnet_receive
> > drivers/net/virtio_net.c:1356 [inline]  
> 
> +virtio maintainers for this one
> Probably something very recent.
> 
> > BUG: KASAN: slab-out-of-bounds in virtnet_poll+0x111a/0x1226
> > drivers/net/virtio_net.c:1421
> > Read of size 8 at addr ffff8801cee08ff0 by task ip/3969
> >
> > CPU: 0 PID: 3969 Comm: ip Not tainted 4.18.0-rc6+ #141
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Call Trace:
> >  <IRQ>
> >  __dump_stack lib/dump_stack.c:77 [inline]
> >  dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
> >  print_address_description+0x6c/0x20b mm/kasan/report.c:256
> >  kasan_report_error mm/kasan/report.c:354 [inline]
> >  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
> >  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
> >  virtnet_receive drivers/net/virtio_net.c:1356 [inline]
> >  virtnet_poll+0x111a/0x1226 drivers/net/virtio_net.c:1421
> >  napi_poll net/core/dev.c:6214 [inline]
> >  net_rx_action+0x7a5/0x1920 net/core/dev.c:6280
> >  __do_softirq+0x2e8/0xb17 kernel/softirq.c:292
> >  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1046
> >  </IRQ>
> >  do_softirq.part.18+0x155/0x1a0 kernel/softirq.c:336
> >  do_softirq arch/x86/include/asm/preempt.h:23 [inline]
> >  __local_bh_enable_ip+0x1ec/0x230 kernel/softirq.c:189
> >  local_bh_enable include/linux/bottom_half.h:32 [inline]
> >  virtnet_napi_enable+0x8c/0xb0 drivers/net/virtio_net.c:1264
> >  virtnet_open+0x16d/0x4d0 drivers/net/virtio_net.c:1464
> >  __dev_open+0x26d/0x410 net/core/dev.c:1392
> >  __dev_change_flags+0x739/0x9c0 net/core/dev.c:7434
> >  dev_change_flags+0x89/0x150 net/core/dev.c:7503
> >  do_setlink+0xb16/0x3dd0 net/core/rtnetlink.c:2416
> >  rtnl_newlink+0x138d/0x1d60 net/core/rtnetlink.c:3029
> >  rtnetlink_rcv_msg+0x46e/0xc30 net/core/rtnetlink.c:4705
> >  netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2447
> >  rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4723
> >  netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
> >  netlink_unicast+0x5a0/0x760 net/netlink/af_netlink.c:1336
> >  netlink_sendmsg+0xa18/0xfc0 net/netlink/af_netlink.c:1901
> >  sock_sendmsg_nosec net/socket.c:641 [inline]
> >  sock_sendmsg+0xd5/0x120 net/socket.c:651
> >  ___sys_sendmsg+0x7fd/0x930 net/socket.c:2125
> >  __sys_sendmsg+0x11d/0x290 net/socket.c:2163
> >  __do_sys_sendmsg net/socket.c:2172 [inline]
> >  __se_sys_sendmsg net/socket.c:2170 [inline]
> >  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2170
> >  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
> >  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > RIP: 0033:0x7f318d594320
> > Code: 02 48 83 c8 ff eb 8d 48 8b 05 14 7b 2a 00 f7 da 64 89 10 48 83 c8 ff
> > eb c9 90 83 3d d5 d2 2a 00 00 75 10 b8 2e 00 00 00 0f 05 <48> 3d 01 f0 ff ff
> > 73 31 c3 48 83 ec 08 e8 5e ba 00 00 48 89 04 24
> > RSP: 002b:00007ffd985d8f38 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> > RAX: ffffffffffffffda RBX: 00007ffd985dd030 RCX: 00007f318d594320
> > RDX: 0000000000000000 RSI: 00007ffd985d8f70 RDI: 0000000000000003
> > RBP: 00007ffd985d8f70 R08: 0000000000000000 R09: 000000000000000f
> > R10: 0000000000000000 R11: 0000000000000246 R12: 000000005b5973aa
> > R13: 0000000000000000 R14: 00000000006395c0 R15: 00007ffd985dd808
> >
> > Allocated by task 1:
> >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
> >  set_track mm/kasan/kasan.c:460 [inline]
> >  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
> >  __do_kmalloc mm/slab.c:3718 [inline]
> >  __kmalloc+0x14e/0x760 mm/slab.c:3727
> >  kmalloc_array include/linux/slab.h:635 [inline]
> >  kcalloc include/linux/slab.h:646 [inline]
> >  virtnet_alloc_queues drivers/net/virtio_net.c:2731 [inline]
> >  init_vqs+0x127/0x1520 drivers/net/virtio_net.c:2769
> >  virtnet_probe+0x1092/0x2260 drivers/net/virtio_net.c:3016
> >  virtio_dev_probe+0x592/0x942 drivers/virtio/virtio.c:245
> >  really_probe drivers/base/dd.c:446 [inline]
> >  driver_probe_device+0x6ad/0x970 drivers/base/dd.c:588
> >  __driver_attach+0x28b/0x2f0 drivers/base/dd.c:822
> >  bus_for_each_dev+0x15d/0x1f0 drivers/base/bus.c:311
> >  driver_attach+0x3d/0x50 drivers/base/dd.c:841
> >  bus_add_driver+0x4b2/0x600 drivers/base/bus.c:667
> >  driver_register+0x1c8/0x320 drivers/base/driver.c:170
> >  register_virtio_driver+0x79/0xd0 drivers/virtio/virtio.c:296
> >  virtio_net_driver_init+0x8d/0xc9 drivers/net/virtio_net.c:3209
> >  do_one_initcall+0x127/0x913 init/main.c:884
> >  do_initcall_level init/main.c:952 [inline]
> >  do_initcalls init/main.c:960 [inline]
> >  do_basic_setup init/main.c:978 [inline]
> >  kernel_init_freeable+0x49b/0x58e init/main.c:1135
> >  kernel_init+0x11/0x1b3 init/main.c:1061
> >  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
> >
> > Freed by task 0:
> > (stack is not available)
> >
> > The buggy address belongs to the object at ffff8801cee08500
> >  which belongs to the cache kmalloc-4096 of size 4096
> > The buggy address is located 2800 bytes inside of
> >  4096-byte region [ffff8801cee08500, ffff8801cee09500)
> > The buggy address belongs to the page:
> > page:ffffea00073b8200 count:1 mapcount:0 mapping:ffff8801dac00dc0 index:0x0
> > compound_mapcount: 0
> > flags: 0x2fffc0000008100(slab|head)
> > raw: 02fffc0000008100 ffffea00073b7d88 ffffea00073b8288 ffff8801dac00dc0
> > raw: 0000000000000000 ffff8801cee08500 0000000100000001 0000000000000000
> > page dumped because: kasan: bad access detected
> >
> > Memory state around the buggy address:
> >  ffff8801cee08e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >  ffff8801cee08f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc  
> >>
> >> ffff8801cee08f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc  
> >
> >                                                              ^
> >  ffff8801cee09000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >  ffff8801cee09080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > ==================================================================
> >
> >
> > ---
> > This bug is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx
> >
> > syzbot will keep track of this bug report. See:
> > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> > syzbot.
> >
> > --
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> > To view this discussion on the web visit
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