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SubjectRe: INFO: trying to register non-static key in l2cap_sock_teardown_cb
From
syzbot has found a reproducer for the following issue on:

HEAD commit: 73b7a604 net: dsa: bcm_sf2: support BCM4908's integrated s..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12ec4a48d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9ce34124da4c882b
dashboard link: https://syzkaller.appspot.com/bug?extid=a41dfef1d2e04910eb2e
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=166ee4cf500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1337172f500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a41dfef1d2e04910eb2e@syzkaller.appspotmail.com

INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.
CPU: 0 PID: 9812 Comm: kworker/0:5 Not tainted 5.11.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events l2cap_chan_timeout
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x107/0x163 lib/dump_stack.c:120
assign_lock_key kernel/locking/lockdep.c:935 [inline]
register_lock_class+0x1041/0x1100 kernel/locking/lockdep.c:1247
__lock_acquire+0x101/0x54f0 kernel/locking/lockdep.c:4711
lock_acquire kernel/locking/lockdep.c:5437 [inline]
lock_acquire+0x29d/0x740 kernel/locking/lockdep.c:5402
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:175
spin_lock_bh include/linux/spinlock.h:359 [inline]
lock_sock_nested+0x3b/0x110 net/core/sock.c:3049
l2cap_sock_teardown_cb+0xa1/0x660 net/bluetooth/l2cap_sock.c:1520
l2cap_chan_del+0xbc/0xa80 net/bluetooth/l2cap_core.c:618
l2cap_chan_close+0x1bc/0xaf0 net/bluetooth/l2cap_core.c:823
l2cap_chan_timeout+0x17e/0x2f0 net/bluetooth/l2cap_core.c:436
process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
kthread+0x3b1/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
==================================================================
BUG: KASAN: use-after-free in l2cap_sock_teardown_cb+0x5c9/0x660 net/bluetooth/l2cap_sock.c:1522
Read of size 8 at addr ffff88802b6ce4c8 by task kworker/0:5/9812

CPU: 0 PID: 9812 Comm: kworker/0:5 Not tainted 5.11.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events l2cap_chan_timeout
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x107/0x163 lib/dump_stack.c:120
print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:230
__kasan_report mm/kasan/report.c:396 [inline]
kasan_report.cold+0x79/0xd5 mm/kasan/report.c:413
l2cap_sock_teardown_cb+0x5c9/0x660 net/bluetooth/l2cap_sock.c:1522
l2cap_chan_del+0xbc/0xa80 net/bluetooth/l2cap_core.c:618
l2cap_chan_close+0x1bc/0xaf0 net/bluetooth/l2cap_core.c:823
l2cap_chan_timeout+0x17e/0x2f0 net/bluetooth/l2cap_core.c:436
process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
kthread+0x3b1/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Allocated by task 8493:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:401 [inline]
____kasan_kmalloc.constprop.0+0x82/0xa0 mm/kasan/common.c:429
kmalloc_node include/linux/slab.h:575 [inline]
kvmalloc_node+0x61/0xf0 mm/util.c:587
kvmalloc include/linux/mm.h:781 [inline]
xt_alloc_table_info+0x3c/0xa0 net/netfilter/x_tables.c:1176
do_replace net/ipv6/netfilter/ip6_tables.c:1141 [inline]
do_ip6t_set_ctl+0x4e5/0xb70 net/ipv6/netfilter/ip6_tables.c:1636
nf_setsockopt+0x83/0xe0 net/netfilter/nf_sockopt.c:101
ipv6_setsockopt+0x122/0x180 net/ipv6/ipv6_sockglue.c:1008
tcp_setsockopt+0x136/0x2440 net/ipv4/tcp.c:3597
__sys_setsockopt+0x2db/0x610 net/socket.c:2115
__do_sys_setsockopt net/socket.c:2126 [inline]
__se_sys_setsockopt net/socket.c:2123 [inline]
__x64_sys_setsockopt+0xba/0x150 net/socket.c:2123
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 8493:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:356
____kasan_slab_free+0xe1/0x110 mm/kasan/common.c:362
kasan_slab_free include/linux/kasan.h:188 [inline]
slab_free_hook mm/slub.c:1547 [inline]
slab_free_freelist_hook+0x5d/0x150 mm/slub.c:1580
slab_free mm/slub.c:3142 [inline]
kfree+0xdb/0x3b0 mm/slub.c:4124
kvfree+0x42/0x50 mm/util.c:616
__do_replace+0x6b7/0x8c0 net/ipv6/netfilter/ip6_tables.c:1103
do_replace net/ipv6/netfilter/ip6_tables.c:1156 [inline]
do_ip6t_set_ctl+0x8ec/0xb70 net/ipv6/netfilter/ip6_tables.c:1636
nf_setsockopt+0x83/0xe0 net/netfilter/nf_sockopt.c:101
ipv6_setsockopt+0x122/0x180 net/ipv6/ipv6_sockglue.c:1008
tcp_setsockopt+0x136/0x2440 net/ipv4/tcp.c:3597
__sys_setsockopt+0x2db/0x610 net/socket.c:2115
__do_sys_setsockopt net/socket.c:2126 [inline]
__se_sys_setsockopt net/socket.c:2123 [inline]
__x64_sys_setsockopt+0xba/0x150 net/socket.c:2123
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff88802b6ce000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1224 bytes inside of
2048-byte region [ffff88802b6ce000, ffff88802b6ce800)
The buggy address belongs to the page:
page:0000000055ddf779 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2b6c8
head:0000000055ddf779 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888010042000
raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88802b6ce380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802b6ce400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802b6ce480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802b6ce500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802b6ce580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

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