Bluetooth: L2cap: use-after-free in l2cap_sock_kill

[Sungwoo Kim]

It is a racy bug between l2cap_chan_timeout() and l2cap_sock_release()
cause by SIGKILL.
Sorry for the less context and no fix here.
For the l2cap_sock.c in the stack trace, please refer this file
for your convenience:
https://gist.github.com/swkim101/5c3b8cb7c7d7172aef23810c9412f323

This is discovered by FuzzBT on top of Syzkaller with Sungwoo Kim (me).
Other contributors for FuzzBT project are Ruoyu Wu(wuruoyu@xxxxxx)
and Hui Peng(benquike@xxxxxxxxx).

==================================================================
BUG: KASAN: use-after-free in l2cap_sock_kill (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/sock.h:986 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1281) 
Read of size 8 at addr ffff88800f7f4060 by task l2cap-server/1764
CPU: 0 PID: 1764 Comm: l2cap-server Not tainted 6.1.0-rc2 #129
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
 <TASK>
dump_stack_lvl (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/lib/dump_stack.c:105) 
print_address_description+0x7e/0x360 
print_report (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report.c:187 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report.c:389) 
? __virt_addr_valid (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/mmzone.h:1855 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/mm/physaddr.c:65) 
? kasan_complete_mode_report_info (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report_generic.c:104 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report_generic.c:127 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report_generic.c:136) 
? l2cap_sock_kill (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/sock.h:986 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1281) 
kasan_report (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report.c:? /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report.c:484) 
? l2cap_sock_kill (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/sock.h:986 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1281) 
kasan_check_range (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:85 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:115 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:128 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:159 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:180 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:189) 
__kasan_check_read (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/shadow.c:31) 
l2cap_sock_kill (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/sock.h:986 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1281) 
l2cap_sock_teardown_cb (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/bluetooth/bluetooth.h:304 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1475 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1612) 
l2cap_chan_close (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:885) 
? __kasan_check_write (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/shadow.c:37) 
l2cap_sock_shutdown (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/kcsan-checks.h:231 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/sock.h:2470 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1321 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1377) 
? _raw_write_unlock (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/asm-generic/qrwlock.h:122 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/rwlock_api_smp.h:225 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/locking/spinlock.c:342) 
l2cap_sock_release (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1453) 
sock_close (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/socket.c:1382) 
? sock_mmap (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/socket.c:?) 
__fput (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/fsnotify.h:? /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/fsnotify.h:99 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/fsnotify.h:341 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/fs/file_table.c:306) 
____fput (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/fs/file_table.c:348) 
task_work_run (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/task_work.c:165) 
do_exit (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/exit.c:?) 
do_group_exit (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/exit.c:943) 
? __kasan_check_write (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/shadow.c:37) 
get_signal (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/signal.c:2863) 
? _raw_spin_unlock (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/spinlock_api_smp.h:142 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/locking/spinlock.c:186) 
? finish_task_switch (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./arch/x86/include/asm/current.h:15 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/sched/core.c:5065) 
arch_do_signal_or_restart (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/kernel/signal.c:869) 
exit_to_user_mode_prepare (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/entry/common.c:383) 
syscall_exit_to_user_mode (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./arch/x86/include/asm/current.h:15 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/entry/common.c:261 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/entry/common.c:283 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/entry/common.c:296) 
do_syscall_64 (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/entry/common.c:50 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/entry/common.c:80) 
? sysvec_apic_timer_interrupt (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/kernel/apic/apic.c:1107) 
entry_SYSCALL_64_after_hwframe (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/entry/entry_64.S:120) 
RIP: 0033:0x7f66c14db970
Code: Unable to access opcode bytes at 0x7f66c14db946.

Code starting with the faulting instruction
===========================================
RSP: 002b:00007ffe166a5508 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: 0000000000000013 RBX: 0000000000000013 RCX: 00007f66c14db970
RDX: 0000000000000013 RSI: 00007ffe166a56d0 RDI: 0000000000000002
RBP: 00007ffe166a56d0 R08: 00007f66c1a28440 R09: 0000000000000013
R10: 0000000000000078 R11: 0000000000000246 R12: 0000000000000013
R13: 0000000000000001 R14: 00007f66c179a520 R15: 0000000000000013
 </TASK>
Allocated by task 77:
kasan_set_track (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/common.c:51) 
kasan_save_alloc_info (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:432 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:498) 
__kasan_kmalloc (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/common.c:356) 
__kmalloc (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slab_common.c:943 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slab_common.c:968) 
sk_prot_alloc (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/core/sock.c:2028) 
sk_alloc (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/core/sock.c:2083) 
l2cap_sock_alloc (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1903) 
l2cap_sock_new_connection_cb (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1504) 
l2cap_connect (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:102 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:4277) 
l2cap_bredr_sig_cmd (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:5634 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:5927) 
l2cap_recv_frame (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:7851 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:7919) 
l2cap_recv_acldata (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:8601 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:8631) 
hci_rx_work (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/bluetooth/hci_core.h:1121 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/hci_core.c:3937 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/hci_core.c:4189) 
process_one_work (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2225) 
worker_thread (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:816 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2107 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2159 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2408) 
kthread (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/kthread.c:361) 
ret_from_fork (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/entry/entry_64.S:306) 
Freed by task 52:
kasan_set_track (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/common.c:51) 
kasan_save_free_info (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:508) 
____kasan_slab_free (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/slub_def.h:164 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/common.c:214) 
__kasan_slab_free (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/common.c:244) 
slab_free_freelist_hook (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slub.c:381 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slub.c:1747) 
__kmem_cache_free (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slub.c:3656 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slub.c:3674) 
kfree (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slab_common.c:1007) 
__sk_destruct (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/cred.h:288 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/core/sock.c:2147) 
__sk_free (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/sock_diag.h:87 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/core/sock.c:2175) 
sk_free (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/instrumented.h:? /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/atomic/atomic-instrumented.h:176 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/refcount.h:272 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/refcount.h:315 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/refcount.h:333 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/core/sock.c:2188) 
l2cap_sock_kill (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/bluetooth/bluetooth.h:286 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1284) 
l2cap_sock_close_cb (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1576) 
l2cap_chan_timeout (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/bluetooth/bluetooth.h:296 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:462) 
process_one_work (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2225) 
worker_thread (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:816 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2107 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2159 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2408) 
kthread (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/kthread.c:361) 
ret_from_fork (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/entry/entry_64.S:306) 
The buggy address belongs to the object at ffff88800f7f4000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 96 bytes inside of
 1024-byte region [ffff88800f7f4000, ffff88800f7f4400)
The buggy address belongs to the physical page:
page:00000000b8d65c1d refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88800f7f6800 pfn:0xf7f4
head:00000000b8d65c1d order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfffffc0010200(slab|head|node=0|zone=1|lastcpupid=0x1fffff)
raw: 000fffffc0010200 ffffea0000993408 ffffea0000991308 ffff888005841dc0
raw: ffff88800f7f6800 0000000000080002 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
 ffff88800f7f3f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88800f7f3f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88800f7f4000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff88800f7f4080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88800f7f4100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================