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BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:183 [inline]
BUG: KASAN: use-after-free in sk_dst_get include/net/sock.h:1764 [inline]
BUG: KASAN: use-after-free in pppol2tp_session_init net/l2tp/l2tp_ppp.c:596 [inline]
BUG: KASAN: use-after-free in pppol2tp_connect+0x1a97/0x1dd0 net/l2tp/l2tp_ppp.c:756
Read of size 8 at addr ffff8801d6326928 by task syz-executor7/12931

CPU: 1 PID: 12931 Comm: syz-executor7 Not tainted 4.15.0-rc8+ #174
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 __read_once_size include/linux/compiler.h:183 [inline]
 sk_dst_get include/net/sock.h:1764 [inline]
 pppol2tp_session_init net/l2tp/l2tp_ppp.c:596 [inline]
 pppol2tp_connect+0x1a97/0x1dd0 net/l2tp/l2tp_ppp.c:756
 SYSC_connect+0x213/0x4a0 net/socket.c:1621
 SyS_connect+0x24/0x30 net/socket.c:1602
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
RIP: 0023:0xf7f12c79
RSP: 002b:00000000f7f0e08c EFLAGS: 00000296 ORIG_RAX: 000000000000016a
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000020e71000
RDX: 0000000000000032 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 12911:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3544
 sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1463
 sk_alloc+0x105/0x1410 net/core/sock.c:1523
 inet6_create+0x44d/0x10f0 net/ipv6/af_inet6.c:183
 __sock_create+0x4d4/0x850 net/socket.c:1267
 sock_create net/socket.c:1307 [inline]
 SYSC_socket net/socket.c:1337 [inline]
 SyS_socket+0xeb/0x1d0 net/socket.c:1317
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129

Freed by task 12931:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3488 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3746
 sk_prot_free net/core/sock.c:1504 [inline]
 __sk_destruct+0x622/0x910 net/core/sock.c:1585
 sk_destruct+0x47/0x80 net/core/sock.c:1593
 __sk_free+0x57/0x230 net/core/sock.c:1601
 sk_free+0x2a/0x40 net/core/sock.c:1612
 sock_put include/net/sock.h:1656 [inline]
 l2tp_session_free+0x21c/0x2b0 net/l2tp/l2tp_core.c:1671
 l2tp_session_dec_refcount net/l2tp/l2tp_core.h:305 [inline]
 pppol2tp_session_destruct+0xd4/0x110 net/l2tp/l2tp_ppp.c:448
 __sk_destruct+0xfd/0x910 net/core/sock.c:1558
 sk_destruct+0x47/0x80 net/core/sock.c:1593
 __sk_free+0x57/0x230 net/core/sock.c:1601
 sk_free+0x2a/0x40 net/core/sock.c:1612
 sock_put include/net/sock.h:1656 [inline]
 pppol2tp_put_sk+0x49/0x60 net/l2tp/l2tp_ppp.c:457
 __rcu_reclaim kernel/rcu/rcu.h:195 [inline]
 rcu_do_batch kernel/rcu/tree.c:2758 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:3012 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2979 [inline]
 rcu_process_callbacks+0xd6c/0x17f0 kernel/rcu/tree.c:2996
 __do_softirq+0x2d7/0xb85 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801d6326700
 which belongs to the cache UDPv6 of size 1664
The buggy address is located 552 bytes inside of
 1664-byte region [ffff8801d6326700, ffff8801d6326d80)
The buggy address belongs to the page:
page:ffffea000758c980 count:1 mapcount:0 mapping:ffff8801d6326000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d6326000 0000000000000000 0000000100000002
raw: ffffea00074f08a0 ffffea000755b7a0 ffff8801d318dcc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d6326800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d6326880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d6326900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8801d6326980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d6326a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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