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BUG: KASAN: use-after-free in tipc_group_bc_cong+0x327/0x3f0 net/tipc/group.c:448
Read of size 2 at addr ffff8881d8a37f74 by task syz-executor530/6024

CPU: 1 PID: 6024 Comm: syz-executor530 Not tainted 4.20.0-rc6-next-20181213+ #170
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+0x244/0x39d lib/dump_stack.c:113
 print_address_description.cold.4+0x9/0x1ff mm/kasan/report.c:187
 kasan_report.cold.5+0x1b/0x39 mm/kasan/report.c:317
 __asan_report_load2_noabort+0x14/0x20 mm/kasan/generic_report.c:133
 tipc_group_bc_cong+0x327/0x3f0 net/tipc/group.c:448
 tipc_send_group_bcast+0x50a/0xd90 net/tipc/socket.c:1023
 __tipc_sendmsg+0xeec/0x1d40 net/tipc/socket.c:1307
 tipc_sendmsg+0x50/0x70 net/tipc/socket.c:1272
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:632
 ___sys_sendmsg+0x7fd/0x930 net/socket.c:2117
 __sys_sendmsg+0x11d/0x280 net/socket.c:2155
 __do_sys_sendmsg net/socket.c:2164 [inline]
 __se_sys_sendmsg net/socket.c:2162 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x446389
Code: e8 2c b3 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 2b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f58fd1f9db8 EFLAGS: 00000297 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000006dac38 RCX: 0000000000446389
RDX: 0000000000000000 RSI: 00000000200006c0 RDI: 0000000000000005
RBP: 00000000006dac30 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 00000000006dac3c
R13: 00007ffd76b851cf R14: 00007f58fd1fa9c0 R15: 00000000006dad2c

Allocated by task 6025:
 save_stack+0x43/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 kasan_kmalloc+0xcb/0xd0 mm/kasan/common.c:482
 kmem_cache_alloc_trace+0x154/0x740 mm/slab.c:3607
 kmalloc include/linux/slab.h:545 [inline]
 kzalloc include/linux/slab.h:740 [inline]
 tipc_group_create+0x152/0xa70 net/tipc/group.c:171
 tipc_sk_join net/tipc/socket.c:2829 [inline]
 tipc_setsockopt+0x2d1/0xd70 net/tipc/socket.c:2944
 __sys_setsockopt+0x1ba/0x3c0 net/socket.c:1903
 __do_sys_setsockopt net/socket.c:1914 [inline]
 __se_sys_setsockopt net/socket.c:1911 [inline]
 __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1911
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 6025:
 save_stack+0x43/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:444
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:452
 __cache_free mm/slab.c:3485 [inline]
 kfree+0xcf/0x230 mm/slab.c:3804
 tipc_group_delete+0x2e4/0x3f0 net/tipc/group.c:227
 tipc_sk_leave+0x113/0x220 net/tipc/socket.c:2863
 tipc_setsockopt+0x97d/0xd70 net/tipc/socket.c:2947
 __sys_setsockopt+0x1ba/0x3c0 net/socket.c:1903
 __do_sys_setsockopt net/socket.c:1914 [inline]
 __se_sys_setsockopt net/socket.c:1911 [inline]
 __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1911
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881d8a37f00
 which belongs to the cache kmalloc-192 of size 192
The buggy address is located 116 bytes inside of
 192-byte region [ffff8881d8a37f00, ffff8881d8a37fc0)
The buggy address belongs to the page:
page:ffffea0007628dc0 count:1 mapcount:0 mapping:ffff8881da800040 index:0x0
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffffea0007603cc8 ffff8881da801148 ffff8881da800040
raw: 0000000000000000 ffff8881d8a37000 0000000100000010 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881d8a37e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881d8a37e80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8881d8a37f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                             ^
 ffff8881d8a37f80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff8881d8a38000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
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