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BUG: KASAN: use-after-free in tipc_group_size+0x40/0x50 net/tipc/group.c:159
Read of size 2 at addr ffff8801d6331e80 by task syzkaller238789/4237

CPU: 1 PID: 4237 Comm: syzkaller238789 Not tainted 4.15.0-rc8+ #263
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_load2_noabort+0x14/0x20 mm/kasan/report.c:428
 tipc_group_size+0x40/0x50 net/tipc/group.c:159
 tipc_poll+0x374/0x4f0 net/tipc/socket.c:739
 sock_poll+0x141/0x320 net/socket.c:1119
 do_pollfd fs/select.c:822 [inline]
 do_poll fs/select.c:872 [inline]
 do_sys_poll+0x715/0x10b0 fs/select.c:966
 SYSC_poll fs/select.c:1024 [inline]
 SyS_poll+0x10d/0x450 fs/select.c:1012
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x44cfd9
RSP: 002b:00007f026ef37ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000007
RAX: ffffffffffffffda RBX: 00000000006f0054 RCX: 000000000044cfd9
RDX: 0000000000007fff RSI: 000000000000000a RDI: 0000000020ef5000
RBP: 00000000006f0050 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000007ff93f R14: 00007f026ef389c0 R15: 0000000000000007

Allocated by task 4236:
 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
 kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610
 kmalloc include/linux/slab.h:499 [inline]
 kzalloc include/linux/slab.h:688 [inline]
 tipc_group_create+0x116/0x9c0 net/tipc/group.c:168
 tipc_sk_join net/tipc/socket.c:2747 [inline]
 tipc_setsockopt+0x249/0xc10 net/tipc/socket.c:2861
 SYSC_setsockopt net/socket.c:1831 [inline]
 SyS_setsockopt+0x189/0x360 net/socket.c:1810
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 4236:
 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]
 kfree+0xd6/0x260 mm/slab.c:3803
 tipc_group_delete+0x2c8/0x3d0 net/tipc/group.c:207
 tipc_sk_join net/tipc/socket.c:2760 [inline]
 tipc_setsockopt+0xb0d/0xc10 net/tipc/socket.c:2861
 SYSC_setsockopt net/socket.c:1831 [inline]
 SyS_setsockopt+0x189/0x360 net/socket.c:1810
 entry_SYSCALL_64_fastpath+0x29/0xa0

The buggy address belongs to the object at ffff8801d6331e00
 which belongs to the cache kmalloc-192 of size 192
The buggy address is located 128 bytes inside of
 192-byte region [ffff8801d6331e00, ffff8801d6331ec0)
The buggy address belongs to the page:
page:ffffea000758cc40 count:1 mapcount:0 mapping:ffff8801d6331000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d6331000 0000000000000000 0000000100000010
raw: ffffea0007549fe0 ffff8801dac01148 ffff8801dac00040 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d6331d80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff8801d6331e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d6331e80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                   ^
 ffff8801d6331f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d6331f80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
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