syzbot

==================================================================
BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
Read of size 4 at addr ffff8800b41baf00 by task syz-executor921/3917

CPU: 0 PID: 3917 Comm: syz-executor921 Not tainted 4.4.152-ge5c5f1f #89
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 a707ab251500d5c5 ffff8801d24a78b0 ffffffff81e15fed
 ffffea0002d06e80 ffff8800b41baf00 0000000000000000 ffff8800b41baf00
 0000000000000000 ffff8801d24a78e8 ffffffff8151b489 ffff8800b41baf00
Call Trace:
 [<ffffffff81e15fed>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e15fed>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8151b489>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff8151b7a8>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8151b7a8>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814fe714>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff835a4b64>] l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
 [<ffffffff835b166f>] pppol2tp_release+0x1ff/0x310 net/l2tp/l2tp_ppp.c:509
 [<ffffffff82f210c9>] __sock_release+0xd9/0x260 net/socket.c:592
 [<ffffffff82f21269>] sock_close+0x19/0x20 net/socket.c:1050
 [<ffffffff81528875>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81528db5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118ee4f>] task_work_run+0x10f/0x190 kernel/task_work.c:115
 [<ffffffff811382b5>] exit_task_work include/linux/task_work.h:21 [inline]
 [<ffffffff811382b5>] do_exit+0x9e5/0x26b0 kernel/exit.c:755
 [<ffffffff8113e1f1>] do_group_exit+0x111/0x330 kernel/exit.c:885
 [<ffffffff811615ec>] get_signal+0x4ec/0x14b0 kernel/signal.c:2321
 [<ffffffff8100df4b>] do_signal+0x8b/0x1d30 arch/x86/kernel/signal.c:712
 [<ffffffff8100360a>] exit_to_usermode_loop+0x11a/0x160 arch/x86/entry/common.c:249
 [<ffffffff81006363>] prepare_exit_to_usermode+0xe3/0x100 arch/x86/entry/common.c:284
 [<ffffffff838cd108>] retint_user+0x8/0x3c

Allocated by task 3914:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd7d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fdab7>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fdab7>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814fa1f4>] __kmalloc+0x124/0x310 mm/slub.c:3613
 [<ffffffff835a9f79>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff835a9f79>] kzalloc include/linux/slab.h:620 [inline]
 [<ffffffff835a9f79>] l2tp_session_create+0x39/0x1030 net/l2tp/l2tp_core.c:1748
 [<ffffffff835aec80>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f27bf8>] SYSC_connect+0x1b8/0x300 net/socket.c:1570
 [<ffffffff82f2a544>] SyS_connect+0x24/0x30 net/socket.c:1551
 [<ffffffff838cc565>] entry_SYSCALL_64_fastpath+0x22/0x9e

Freed by task 3895:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd7d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fe102>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fe102>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814fb664>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814fb664>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814fb664>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814fb664>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff835a6ee0>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1676
 [<ffffffff835a9299>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline]
 [<ffffffff835a9299>] l2tp_tunnel_closeall+0x2b9/0x350 net/l2tp/l2tp_core.c:1279
 [<ffffffff835a9dab>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff8349bc11>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421
 [<ffffffff82f38add>] sk_common_release+0x6d/0x300 net/core/sock.c:2680
 [<ffffffff8349a8c5>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff8330244f>] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff83424ec0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82f210c9>] __sock_release+0xd9/0x260 net/socket.c:592
 [<ffffffff82f21269>] sock_close+0x19/0x20 net/socket.c:1050
 [<ffffffff81528875>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81528db5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118ee4f>] task_work_run+0x10f/0x190 kernel/task_work.c:115
 [<ffffffff811382b5>] exit_task_work include/linux/task_work.h:21 [inline]
 [<ffffffff811382b5>] do_exit+0x9e5/0x26b0 kernel/exit.c:755
 [<ffffffff8113e1f1>] do_group_exit+0x111/0x330 kernel/exit.c:885
 [<ffffffff811615ec>] get_signal+0x4ec/0x14b0 kernel/signal.c:2321
 [<ffffffff8100df4b>] do_signal+0x8b/0x1d30 arch/x86/kernel/signal.c:712
 [<ffffffff8100360a>] exit_to_usermode_loop+0x11a/0x160 arch/x86/entry/common.c:249
 [<ffffffff81006363>] prepare_exit_to_usermode+0xe3/0x100 arch/x86/entry/common.c:284
 [<ffffffff838cd108>] retint_user+0x8/0x3c

The buggy address belongs to the object at ffff8800b41baf00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8800b41baf00, ffff8800b41bb100)
The buggy address belongs to the page:
Initializing cgroup subsys cpuset
Initializing cgroup subsys cpu
Initializing cgroup subsys cpuacct
Initializing cgroup subsys schedtune
Linux version 4.4.152-ge5c5f1f (syzkaller@ci) (gcc version 8.0.1 20180413 (experimental) (GCC) ) #89 SMP PREEMPT Sat Aug 25 06:48:55 UTC 2018
Command line: BOOT_IMAGE=/vmlinuz root=/dev/sda1 console=ttyS0 earlyprintk=serial vsyscall=native rodata=n ftrace_dump_on_oops=orig_cpu oops=panic panic_on_warn=1 nmi_watchdog=panic panic=86400 workqueue.watchdog_thresh=140 nopti
KERNEL supported cpus:
  Intel GenuineIntel
  AMD AuthenticAMD
  Centaur CentaurHauls
x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
x86/fpu: Supporting XSAVE feature 0x01: 'x87 floating point registers'
x86/fpu: Supporting XSAVE feature 0x02: 'SSE registers'
x86/fpu: Supporting XSAVE feature 0x04: 'AVX registers'
x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'standard' format.
e820: BIOS-provided physical RAM map:
BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
BIOS-e820: [mem 0x0000000000100000-0x00000000bfff2fff] usable
BIOS-e820: [mem 0x00000000bfff3000-0x00000000bfffffff] reserved
BIOS-e820: [mem 0x00000000fffbc000-0x00000000ffffffff] reserved
BIOS-e820: [mem 0x0000000100000000-0x000000021fffffff] usable
bootconsole [earlyser0] enabled
NX (Execute Disable) protection: active
SMBIOS 2.4 present.
Hypervisor detected: KVM
Kernel/User page tables isolation: disabled
e820: last_pfn = 0x220000 max_arch_pfn = 0x400000000
x86/PAT: Configuration [0-7]: WB  WC  UC- UC  WB  WC  UC- WT  
e820: last_pfn = 0xbfff3 max_arch_pfn = 0x400000000
found SMP MP-table at [mem 0x000f2300-0x000f230f] mapped at [ffff8800000f2300]
Scanning 1 areas for low memory corruption
Using GB pages for direct mapping
ACPI: Early table checksum verification disabled
ACPI: RSDP 0x00000000000F22C0 000014 (v00 Google)
ACPI: RSDT 0x00000000BFFF3430 000038 (v01 Google GOOGRSDT 00000001 GOOG 00000001)
ACPI: FACP 0x00000000BFFFCF60 0000F4 (v02 Google GOOGFACP 00000001 GOOG 00000001)
ACPI: DSDT 0x00000000BFFF3470 0017B2 (v01 Google GOOGDSDT 00000001 GOOG 00000001)
ACPI: FACS 0x00000000BFFFCF00 000040
ACPI: FACS 0x00000000BFFFCF00 000040
ACPI: SSDT 0x00000000BFFF65F0 00690D (v01 Google GOOGSSDT 00000001 GOOG 00000001)
ACPI: APIC 0x00000000BFFF5D10 000076 (v01 Google GOOGAPIC 00000001 GOOG 00000001)
ACPI: WAET 0x00000000BFFF5CE0 000028 (v01 Google GOOGWAET 00000001 GOOG 00000001)
ACPI: SRAT 0x00000000BFFF4C30 0000C8 (v01 Google GOOGSRAT 00000001 GOOG 00000001)
kvm-clock: Using msrs 4b564d01 and 4b564d00
kvm-clock: cpu 0, msr 2:1fffd001, primary cpu clock
kvm-clock: using sched offset of 2243076387 cycles
clocksource: kvm-clock: mask: 0xffffffffffffffff max_cycles: 0x1cd42e4dffb, max_idle_ns: 881590591483 ns
Zone ranges:
  DMA      [mem 0x0000000000001000-0x0000000000ffffff]
  DMA32    [mem 0x0000000001000000-0x00000000ffffffff]
  Normal   [mem 0x0000000100000000-0x000000021fffffff]
Movable zone start for each node
Early memory node ranges
  node   0: [mem 0x0000000000001000-0x000000000009efff]
  node   0: [mem 0x0000000000100000-0x00000000bfff2fff]
  node   0: [mem 0x0000000100000000-0x000000021fffffff]
Initmem setup node 0 [mem 0x0000000000001000-0x000000021fffffff]
kasan: KernelAddressSanitizer initialized
ACPI: PM-Timer IO Port: 0xb008
ACPI: LAPIC_NMI (acpi_id[0xff] dfl dfl lint[0x1])
IOAPIC[0]: apic_id 0, version 17, address 0xfec00000, GSI 0-23
ACPI: INT_SRC_OVR (bus 0 bus_irq 5 global_irq 5 high level)
ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level)
ACPI: INT_SRC_OVR (bus 0 bus_irq 10 global_irq 10 high level)
ACPI: INT_SRC_OVR (bus 0 bus_irq 11 global_irq 11 high level)
Using ACPI (MADT) for SMP configuration information
smpboot: Allowing 2 CPUs, 0 hotplug CPUs
PM: Registered nosave memory: [mem 0x00000000-0x00000fff]
PM: Registered nosave memory: [mem 0x0009f000-0x0009ffff]
PM: Registered nosave memory: [mem 0x000a0000-0x000effff]
PM: Registered nosave memory: [mem 0x000f0000-0x000fffff]
PM: Registered nosave memory: [mem 0xbfff3000-0xbfffffff]
PM: Registered nosave memory: [mem 0xc0000000-0xfffbbfff]
PM: Registered nosave memory: [mem 0xfffbc000-0xffffffff]
e820: [mem 0xc0000000-0xfffbbfff] available for PCI devices
Booting paravirtualized kernel on KVM
clocksource: refined-jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
setup_percpu: NR_CPUS:64 nr_cpumask_bits:64 nr_cpu_ids:2 nr_node_ids:1
PERCPU: Embedded 42 pages/cpu @ffff8801db200000 s134152 r8192 d29688 u1048576
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 1935227
Kernel command line: BOOT_IMAGE=/vmlinuz root=/dev/sda1 console=ttyS0 earlyprintk=serial vsyscall=native rodata=n ftrace_dump_on_oops=orig_cpu oops=panic panic_on_warn=1 nmi_watchdog=panic panic=86400 workqueue.watchdog_thresh=140 nopti
PID hash table entries: 4096 (order: 3, 32768 bytes)
Dentry cache hash table entries: 1048576 (order: 11, 8388608 bytes)
Inode-cache hash table entries: 524288 (order: 10, 4194304 bytes)
Memory: 6579080K/7863876K available (41801K kernel code, 6308K rwdata, 9068K rodata, 1868K init, 23696K bss, 1284796K reserved, 0K cma-reserved)
SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=2, Nodes=1
Running RCU self tests
Preemptible hierarchical RCU implementation.
	RCU lockdep checking is enabled.
	Build-time adjustment of leaf fanout to 64.
	RCU restricting CPUs from NR_CPUS=64 to nr_cpu_ids=2.
RCU: Adjusting geometry for rcu_fanout_leaf=64, nr_cpu_ids=2
NR_IRQS:4352 nr_irqs:440 16
console [ttyS0] enabled
console [ttyS0] enabled
bootconsole [earlyser0] disabled
bootconsole [earlyser0] disabled
Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar
... MAX_LOCKDEP_SUBCLASSES:  8
... MAX_LOCK_DEPTH:          48
... MAX_LOCKDEP_KEYS:        8191
... CLASSHASH_SIZE:          4096
... MAX_LOCKDEP_ENTRIES:     32768
... MAX_LOCKDEP_CHAINS:      65536
... CHAINHASH_SIZE:          32768
 memory used by lock dependency info: 8159 kB
 per task-struct memory footprint: 1920 bytes
tsc: Detected 2299.998 MHz processor
Calibrating delay loop (skipped) preset value.. 4599.99 BogoMIPS (lpj=22999980)
pid_max: default: 32768 minimum: 301
ACPI: Core revision 20150930
ACPI: 2 ACPI AML tables successfully acquired and loaded
Security Framework initialized
SELinux:  Initializing.
AppArmor: AppArmor disabled by boot time parameter
Mount-cache hash table entries: 16384 (order: 5, 131072 bytes)
Mountpoint-cache hash table entries: 16384 (order: 5, 131072 bytes)
Initializing cgroup subsys io
Initializing cgroup subsys freezer
Initializing cgroup subsys hugetlb
Initializing cgroup subsys debug
CPU: Physical Processor ID: 0
mce: CPU supports 32 MCE banks
Last level iTLB entries: 4KB 1024, 2MB 1024, 4MB 1024
Last level dTLB entries: 4KB 1024, 2MB 1024, 4MB 1024, 1GB 4
Spectre V2 : Mitigation: Full generic retpoline
Spectre V2 : Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch
Speculative Store Bypass: Vulnerable
Freeing SMP alternatives memory: 48K
..TIMER: vector=0x30 apic1=0 pin1=0 apic2=-1 pin2=-1
smpboot: CPU0: Intel(R) Xeon(R) CPU @ 2.30GHz (family: 0x6, model: 0x3f, stepping: 0x0)
Performance Events: unsupported p6 CPU model 63 no PMU driver, software events only.
x86: Booting SMP configuration:
.... node  #0, CPUs:      #1
kvm-clock: cpu 1, msr 2:1fffd041, secondary cpu clock
x86: Booted up 1 node, 2 CPUs
smpboot: Total of 2 processors activated (9199.99 BogoMIPS)
devtmpfs: initialized
clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
futex hash table entries: 512 (order: 4, 65536 bytes)
xor: automatically using best checksumming function:
kworker/u4:0 (21) used greatest stack depth: 27920 bytes left
   avx       : 25388.000 MB/sec
RTC time:  1:16:22, date: 08/27/18
NET: Registered protocol family 16
schedtune: init normalization constants...
schedtune: no energy model data
schedtune: disabled!
kworker/u4:0 (27) used greatest stack depth: 27664 bytes left
cpuidle: using governor ladder
cpuidle: using governor menu
ACPI: bus type PCI registered
acpiphp: ACPI Hot Plug PCI Controller Driver version: 0.5
PCI: Using configuration type 1 for base access
kworker/u4:0 (43) used greatest stack depth: 27616 bytes left
kworker/u4:0 (46) used greatest stack depth: 27424 bytes left
kworker/u4:0 (47) used greatest stack depth: 27024 bytes left
raid6: sse2x1   gen()  4434 MB/s
raid6: sse2x1   xor()  2350 MB/s
raid6: sse2x2   gen()  6828 MB/s
raid6: sse2x2   xor()  3922 MB/s
raid6: sse2x4   gen()  9569 MB/s
raid6: sse2x4   xor()  5450 MB/s
raid6: avx2x1   gen()  9393 MB/s
raid6: avx2x2   gen() 13206 MB/s
raid6: avx2x4   gen() 17901 MB/s
raid6: using algorithm avx2x4 gen() 17901 MB/s
raid6: using avx2x2 recovery algorithm
ACPI: Added _OSI(Module Device)
ACPI: Added _OSI(Processor Device)
ACPI: Added _OSI(3.0 _SCP Extensions)
ACPI: Added _OSI(Processor Aggregator Device)
ACPI: Executed 2 blocks of module-level executable AML code
ACPI: Interpreter enabled
ACPI: (supports S0 S3 S4 S5)
ACPI: Using IOAPIC for interrupt routing
PCI: Using host bridge windows from ACPI; if necessary, use "pci=nocrs" and report a bug
ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff])
acpi PNP0A03:00: _OSC: OS supports [ASPM ClockPM Segments MSI]
acpi PNP0A03:00: _OSC failed (AE_NOT_FOUND); disabling ASPM
acpi PNP0A03:00: fail to add MMCONFIG information, can't access extended PCI configuration space under this bridge.
PCI host bridge to bus 0000:00
pci_bus 0000:00: root bus resource [io  0x0000-0x0cf7 window]
pci_bus 0000:00: root bus resource [io  0x0d00-0xffff window]
pci_bus 0000:00: root bus resource [mem 0x000a0000-0x000bffff window]
pci_bus 0000:00: root bus resource [mem 0xc0000000-0xfebfffff window]
pci_bus 0000:00: root bus resource [bus 00-ff]
pci 0000:00:01.3: quirk: [io  0xb000-0xb03f] claimed by PIIX4 ACPI
ACPI: PCI Interrupt Link [LNKA] (IRQs 5 *10 11)
ACPI: PCI Interrupt Link [LNKB] (IRQs 5 *10 11)
ACPI: PCI Interrupt Link [LNKC] (IRQs 5 10 *11)
ACPI: PCI Interrupt Link [LNKD] (IRQs 5 10 *11)
ACPI: PCI Interrupt Link [LNKS] (IRQs *9)