BUG: unable to handle kernel NULL pointer dereference in l2cap_sock_teardown_cb

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7cca308cfdc0 Merge tag 'powerpc-5.15-1' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=122210c9300000
kernel config: https://syzkaller.appspot.com/x/.config?x=9c582b69de20dde2
dashboard link: https://syzkaller.appspot.com/bug?extid=f8cbd98b1ad2ac371025
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
CC: [da...@davemloft.net johan....@gmail.com ku...@kernel.org linux-b...@vger.kernel.org linux-...@vger.kernel.org luiz....@gmail.com mar...@holtmann.org net...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f8cbd9...@syzkaller.appspotmail.com

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 74724067 P4D 74724067 PUD 74725067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 22487 Comm: syz-executor.5 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc9000171f880 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff888085e8d000 RCX: 0000000000000000
RDX: 1ffff11010bd1a8d RSI: ffffffff8824748b RDI: ffff888085e8d000
RBP: 0000000000000000 R08: ffffffff8aa1ebe0 R09: ffffffff882470f6
R10: 0000000000000004 R11: 0000000000000005 R12: 0000000000000067
R13: ffff888085e8a000 R14: ffff888085e8a4b8 R15: 0000000000000067
FS: 0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000020d53000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
l2cap_sock_teardown_cb+0x496/0x660 net/bluetooth/l2cap_sock.c:1553
l2cap_chan_del+0xbc/0xa80 net/bluetooth/l2cap_core.c:622
l2cap_conn_del+0x3c0/0x7b0 net/bluetooth/l2cap_core.c:1898
l2cap_disconn_cfm net/bluetooth/l2cap_core.c:8177 [inline]
l2cap_disconn_cfm+0x95/0xd0 net/bluetooth/l2cap_core.c:8170
hci_disconn_cfm include/net/bluetooth/hci_core.h:1518 [inline]
hci_conn_hash_flush+0x127/0x260 net/bluetooth/hci_conn.c:1608
hci_dev_do_close+0x57d/0x1130 net/bluetooth/hci_core.c:1793
hci_unregister_dev+0x1c0/0x5a0 net/bluetooth/hci_core.c:4029
vhci_release+0x70/0xe0 drivers/bluetooth/hci_vhci.c:340
__fput+0x288/0x9f0 fs/file_table.c:280
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
exit_task_work include/linux/task_work.h:32 [inline]
do_exit+0xbae/0x2a30 kernel/exit.c:825
do_group_exit+0x125/0x310 kernel/exit.c:922
get_signal+0x47f/0x2160 kernel/signal.c:2868
arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:865
handle_signal_work kernel/entry/common.c:148 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:209
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665f9
Code: Unable to access opcode bytes at RIP 0x4665cf.
RSP: 002b:00007ffb75b11218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000056bf88 RCX: 00000000004665f9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000056bf88
RBP: 000000000056bf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf8c
R13: 00007ffe9f1fd46f R14: 00007ffb75b11300 R15: 0000000000022000
Modules linked in:
CR2: 0000000000000000
---[ end trace 441200ec765b44cf ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc9000171f880 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff888085e8d000 RCX: 0000000000000000
RDX: 1ffff11010bd1a8d RSI: ffffffff8824748b RDI: ffff888085e8d000
RBP: 0000000000000000 R08: ffffffff8aa1ebe0 R09: ffffffff882470f6
R10: 0000000000000004 R11: 0000000000000005 R12: 0000000000000067
R13: ffff888085e8a000 R14: ffff888085e8a4b8 R15: 0000000000000067
FS: 0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000020d53000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.