KASAN: use-after-free Read in tipc_group_bc_cong

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 0844895a2e51 Merge tag 'char-misc-4.20-rc6' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=153c1925400000
kernel config: https://syzkaller.appspot.com/x/.config?x=8110fb1cd164e8f
dashboard link: https://syzkaller.appspot.com/bug?extid=10a9db47c3a0e13eb31c
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=177a927d400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11b59da3400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+10a9db...@syzkaller.appspotmail.com

audit: type=1400 audit(1544417020.270:36): avc: denied { map } for
pid=6121 comm="syz-executor870" path="/root/syz-executor870904155"
dev="sda1" ino=16484 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: use-after-free in tipc_group_bc_cong+0x327/0x3f0
net/tipc/group.c:448
Read of size 2 at addr ffff8881d7bc1674 by task syz-executor870/6139

CPU: 0 PID: 6139 Comm: syz-executor870 Not tainted 4.20.0-rc5+ #149
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.7+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
__asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:431
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:621 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:631
___sys_sendmsg+0x51d/0x930 net/socket.c:2116
__sys_sendmmsg+0x246/0x6d0 net/socket.c:2211
__do_sys_sendmmsg net/socket.c:2240 [inline]
__se_sys_sendmmsg net/socket.c:2237 [inline]
__x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2237
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x446339
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:00007ff1bd83bdb8 EFLAGS: 00000297 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00000000006dac38 RCX: 0000000000446339
RDX: 0000000000000142 RSI: 0000000020000000 RDI: 0000000000000006
RBP: 00000000006dac30 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 00000000006dac3c
R13: 00007ffea6d1565f R14: 00007ff1bd83c9c0 R15: 00000000006dad2c

Allocated by task 6139:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
kmalloc include/linux/slab.h:546 [inline]
kzalloc include/linux/slab.h:741 [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:1902
__do_sys_setsockopt net/socket.c:1913 [inline]
__se_sys_setsockopt net/socket.c:1910 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:1910
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 6140:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3817
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:1902
__do_sys_setsockopt net/socket.c:1913 [inline]
__se_sys_setsockopt net/socket.c:1910 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:1910
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 ffff8881d7bc1600
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 116 bytes inside of
192-byte region [ffff8881d7bc1600, ffff8881d7bc16c0)
The buggy address belongs to the page:
page:ffffea00075ef040 count:1 mapcount:0 mapping:ffff8881da800040 index:0x0
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffffea00075e7e88 ffffea00075d5c08 ffff8881da800040
raw: 0000000000000000 ffff8881d7bc1000 0000000100000010 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881d7bc1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881d7bc1580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ffff8881d7bc1600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881d7bc1680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8881d7bc1700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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