[v5.15] possible deadlock in rfcomm_dlc_exists

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syzbot

unread,
Mar 23, 2023, 5:28:51 PM3/23/23
to syzkaller...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: 115472395b0a Linux 5.15.104
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1121e69ac80000
kernel config: https://syzkaller.appspot.com/x/.config?x=f5592cc4916e1c2f
dashboard link: https://syzkaller.appspot.com/bug?extid=de82738425bd819f2b1e
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6c2c0744c7e0/disk-11547239.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7ea4c5ecca4f/vmlinux-11547239.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9a231dbcf423/bzImage-11547239.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+de8273...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.15.104-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/25039 is trying to acquire lock:
ffffffff8db3c2e8 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_exists+0xa2/0x370 net/bluetooth/rfcomm/core.c:542

but task is already holding lock:
ffffffff8db3fcc8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_create_dev net/bluetooth/rfcomm/tty.c:485 [inline]
ffffffff8db3fcc8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_dev_ioctl+0x233/0x2180 net/bluetooth/rfcomm/tty.c:588

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (rfcomm_ioctl_mutex){+.+.}-{3:3}:
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
__mutex_lock_common+0x1da/0x25a0 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
rfcomm_create_dev net/bluetooth/rfcomm/tty.c:485 [inline]
rfcomm_dev_ioctl+0x233/0x2180 net/bluetooth/rfcomm/tty.c:588
rfcomm_sock_ioctl+0x82/0xc0 net/bluetooth/rfcomm/sock.c:880
sock_do_ioctl+0x11d/0x5a0 net/socket.c:1121
sock_ioctl+0x47f/0x770 net/socket.c:1238
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb

-> #2 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}:
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
lock_sock_nested+0x44/0x100 net/core/sock.c:3216
lock_sock include/net/sock.h:1649 [inline]
rfcomm_sk_state_change+0x57/0x300 net/bluetooth/rfcomm/sock.c:73
__rfcomm_dlc_close+0x2b2/0x6d0 net/bluetooth/rfcomm/core.c:489
rfcomm_dlc_close+0xed/0x180 net/bluetooth/rfcomm/core.c:520
__rfcomm_sock_close+0x104/0x220 net/bluetooth/rfcomm/sock.c:220
rfcomm_sock_shutdown+0xb4/0x230 net/bluetooth/rfcomm/sock.c:912
__sys_shutdown_sock net/socket.c:2251 [inline]
__sys_shutdown net/socket.c:2263 [inline]
__do_sys_shutdown net/socket.c:2271 [inline]
__se_sys_shutdown+0x147/0x1a0 net/socket.c:2269
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb

-> #1 (&d->lock){+.+.}-{3:3}:
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
__mutex_lock_common+0x1da/0x25a0 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
__rfcomm_dlc_close+0x259/0x6d0 net/bluetooth/rfcomm/core.c:487
rfcomm_dlc_close+0xed/0x180 net/bluetooth/rfcomm/core.c:520
__rfcomm_sock_close+0x104/0x220 net/bluetooth/rfcomm/sock.c:220
rfcomm_sock_shutdown+0xb4/0x230 net/bluetooth/rfcomm/sock.c:912
__sys_shutdown_sock net/socket.c:2251 [inline]
__sys_shutdown net/socket.c:2263 [inline]
__do_sys_shutdown net/socket.c:2271 [inline]
__se_sys_shutdown+0x147/0x1a0 net/socket.c:2269
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb

-> #0 (rfcomm_mutex){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1646/0x58b0 kernel/locking/lockdep.c:3787
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5011
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
__mutex_lock_common+0x1da/0x25a0 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
rfcomm_dlc_exists+0xa2/0x370 net/bluetooth/rfcomm/core.c:542
__rfcomm_create_dev net/bluetooth/rfcomm/tty.c:415 [inline]
rfcomm_create_dev net/bluetooth/rfcomm/tty.c:486 [inline]
rfcomm_dev_ioctl+0xb2d/0x2180 net/bluetooth/rfcomm/tty.c:588
rfcomm_sock_ioctl+0x82/0xc0 net/bluetooth/rfcomm/sock.c:880
sock_do_ioctl+0x11d/0x5a0 net/socket.c:1121
sock_ioctl+0x47f/0x770 net/socket.c:1238
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb

other info that might help us debug this:

Chain exists of:
rfcomm_mutex --> sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM --> rfcomm_ioctl_mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(rfcomm_ioctl_mutex);
lock(sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM);
lock(rfcomm_ioctl_mutex);
lock(rfcomm_mutex);

*** DEADLOCK ***

2 locks held by syz-executor.0/25039:
#0: ffff888022ceb120 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1649 [inline]
#0: ffff888022ceb120 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_ioctl+0x74/0xc0 net/bluetooth/rfcomm/sock.c:879
#1: ffffffff8db3fcc8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_create_dev net/bluetooth/rfcomm/tty.c:485 [inline]
#1: ffffffff8db3fcc8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_dev_ioctl+0x233/0x2180 net/bluetooth/rfcomm/tty.c:588

stack backtrace:
CPU: 1 PID: 25039 Comm: syz-executor.0 Not tainted 5.15.104-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
check_noncircular+0x2f8/0x3b0 kernel/locking/lockdep.c:2133
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1646/0x58b0 kernel/locking/lockdep.c:3787
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5011
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
__mutex_lock_common+0x1da/0x25a0 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
rfcomm_dlc_exists+0xa2/0x370 net/bluetooth/rfcomm/core.c:542
__rfcomm_create_dev net/bluetooth/rfcomm/tty.c:415 [inline]
rfcomm_create_dev net/bluetooth/rfcomm/tty.c:486 [inline]
rfcomm_dev_ioctl+0xb2d/0x2180 net/bluetooth/rfcomm/tty.c:588
rfcomm_sock_ioctl+0x82/0xc0 net/bluetooth/rfcomm/sock.c:880
sock_do_ioctl+0x11d/0x5a0 net/socket.c:1121
sock_ioctl+0x47f/0x770 net/socket.c:1238
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f443c9d10f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f443aee0168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f443caf11f0 RCX: 00007f443c9d10f9
RDX: 0000000020000100 RSI: 00000000400452c8 RDI: 000000000000000a
RBP: 00007f443ca2cb39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd0cc0142f R14: 00007f443aee0300 R15: 0000000000022000
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

syzbot

unread,
Mar 23, 2023, 11:20:44 PM3/23/23
to syzkaller...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: e3a87a10f259 Linux 6.1.21
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17a736eec80000
kernel config: https://syzkaller.appspot.com/x/.config?x=b49b0405a60858ed
dashboard link: https://syzkaller.appspot.com/bug?extid=8e4c71cb4113a8a02b5b
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ed3d1f3e75e6/disk-e3a87a10.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6d8e44c8c75c/vmlinux-e3a87a10.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cebe803ea4fa/bzImage-e3a87a10.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8e4c71...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.1.21-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.3/11327 is trying to acquire lock:
ffffffff8e204ac8 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_exists+0xa2/0x370 net/bluetooth/rfcomm/core.c:542

but task is already holding lock:
ffffffff8e2084c8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_create_dev net/bluetooth/rfcomm/tty.c:484 [inline]
ffffffff8e2084c8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_dev_ioctl+0x233/0x2180 net/bluetooth/rfcomm/tty.c:587

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (rfcomm_ioctl_mutex){+.+.}-{3:3}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
__mutex_lock_common+0x1d4/0x2520 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
rfcomm_create_dev net/bluetooth/rfcomm/tty.c:484 [inline]
rfcomm_dev_ioctl+0x233/0x2180 net/bluetooth/rfcomm/tty.c:587
rfcomm_sock_ioctl+0x82/0xc0 net/bluetooth/rfcomm/sock.c:880
sock_do_ioctl+0x152/0x450 net/socket.c:1174
sock_ioctl+0x47f/0x770 net/socket.c:1291
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #2 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
lock_sock_nested+0x44/0x100 net/core/sock.c:3458
lock_sock include/net/sock.h:1721 [inline]
rfcomm_sk_state_change+0x57/0x300 net/bluetooth/rfcomm/sock.c:73
__rfcomm_dlc_close+0x2b2/0x6d0 net/bluetooth/rfcomm/core.c:489
rfcomm_dlc_close+0xed/0x180 net/bluetooth/rfcomm/core.c:520
__rfcomm_sock_close+0x104/0x220 net/bluetooth/rfcomm/sock.c:220
rfcomm_sock_shutdown+0xb4/0x230 net/bluetooth/rfcomm/sock.c:912
__sys_shutdown_sock net/socket.c:2324 [inline]
__sys_shutdown net/socket.c:2336 [inline]
__do_sys_shutdown net/socket.c:2344 [inline]
__se_sys_shutdown+0x147/0x1a0 net/socket.c:2342
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #1 (&d->lock){+.+.}-{3:3}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
__mutex_lock_common+0x1d4/0x2520 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
__rfcomm_dlc_close+0x259/0x6d0 net/bluetooth/rfcomm/core.c:487
rfcomm_dlc_close+0xed/0x180 net/bluetooth/rfcomm/core.c:520
__rfcomm_sock_close+0x104/0x220 net/bluetooth/rfcomm/sock.c:220
rfcomm_sock_shutdown+0xb4/0x230 net/bluetooth/rfcomm/sock.c:912
__sys_shutdown_sock net/socket.c:2324 [inline]
__sys_shutdown net/socket.c:2336 [inline]
__do_sys_shutdown net/socket.c:2344 [inline]
__se_sys_shutdown+0x147/0x1a0 net/socket.c:2342
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (rfcomm_mutex){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3098 [inline]
check_prevs_add kernel/locking/lockdep.c:3217 [inline]
validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
__mutex_lock_common+0x1d4/0x2520 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
rfcomm_dlc_exists+0xa2/0x370 net/bluetooth/rfcomm/core.c:542
__rfcomm_create_dev net/bluetooth/rfcomm/tty.c:414 [inline]
rfcomm_create_dev net/bluetooth/rfcomm/tty.c:485 [inline]
rfcomm_dev_ioctl+0xb2d/0x2180 net/bluetooth/rfcomm/tty.c:587
rfcomm_sock_ioctl+0x82/0xc0 net/bluetooth/rfcomm/sock.c:880
sock_do_ioctl+0x152/0x450 net/socket.c:1174
sock_ioctl+0x47f/0x770 net/socket.c:1291
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Chain exists of:
rfcomm_mutex --> sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM --> rfcomm_ioctl_mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(rfcomm_ioctl_mutex);
lock(sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM);
lock(rfcomm_ioctl_mutex);
lock(rfcomm_mutex);

*** DEADLOCK ***

2 locks held by syz-executor.3/11327:
#0: ffff88803bd72130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1721 [inline]
#0: ffff88803bd72130 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_ioctl+0x74/0xc0 net/bluetooth/rfcomm/sock.c:879
#1: ffffffff8e2084c8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_create_dev net/bluetooth/rfcomm/tty.c:484 [inline]
#1: ffffffff8e2084c8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_dev_ioctl+0x233/0x2180 net/bluetooth/rfcomm/tty.c:587

stack backtrace:
CPU: 1 PID: 11327 Comm: syz-executor.3 Not tainted 6.1.21-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
check_noncircular+0x2fa/0x3b0 kernel/locking/lockdep.c:2178
check_prev_add kernel/locking/lockdep.c:3098 [inline]
check_prevs_add kernel/locking/lockdep.c:3217 [inline]
validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
__mutex_lock_common+0x1d4/0x2520 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
rfcomm_dlc_exists+0xa2/0x370 net/bluetooth/rfcomm/core.c:542
__rfcomm_create_dev net/bluetooth/rfcomm/tty.c:414 [inline]
rfcomm_create_dev net/bluetooth/rfcomm/tty.c:485 [inline]
rfcomm_dev_ioctl+0xb2d/0x2180 net/bluetooth/rfcomm/tty.c:587
rfcomm_sock_ioctl+0x82/0xc0 net/bluetooth/rfcomm/sock.c:880
sock_do_ioctl+0x152/0x450 net/socket.c:1174
sock_ioctl+0x47f/0x770 net/socket.c:1291
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f181608c0f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f18149bc168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f18161ac1f0 RCX: 00007f181608c0f9
RDX: 0000000020000100 RSI: 00000000400452c8 RDI: 000000000000000a
RBP: 00007f18160e7b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff0b522c3f R14: 00007f18149bc300 R15: 0000000000022000

syzbot

unread,
Apr 24, 2024, 4:36:24 AMApr 24
to syzkaller...@googlegroups.com
syzbot has found a reproducer for the following issue on:

HEAD commit: c52b9710c83d Linux 5.15.156
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=119e4bf7180000
kernel config: https://syzkaller.appspot.com/x/.config?x=41e09ec50c6bb4e4
dashboard link: https://syzkaller.appspot.com/bug?extid=de82738425bd819f2b1e
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=139a83fd180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12ff5ae7180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/586695cf1548/disk-c52b9710.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/10a68b27874f/vmlinux-c52b9710.xz
kernel image: https://storage.googleapis.com/syzbot-assets/610e1be513a8/Image-c52b9710.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+de8273...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.15.156-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor281/3988 is trying to acquire lock:
ffff800016b98b68 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_exists+0xb0/0x32c net/bluetooth/rfcomm/core.c:542

but task is already holding lock:
ffff800016b9c4c8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_create_dev net/bluetooth/rfcomm/tty.c:485 [inline]
ffff800016b9c4c8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_dev_ioctl+0x258/0x2434 net/bluetooth/rfcomm/tty.c:588

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (rfcomm_ioctl_mutex){+.+.}-{3:3}:
__mutex_lock_common+0x194/0x2154 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0xa4/0xf8 kernel/locking/mutex.c:743
rfcomm_create_dev net/bluetooth/rfcomm/tty.c:485 [inline]
rfcomm_dev_ioctl+0x258/0x2434 net/bluetooth/rfcomm/tty.c:588
rfcomm_sock_ioctl+0x98/0xf0 net/bluetooth/rfcomm/sock.c:880
sock_do_ioctl+0x134/0x2dc net/socket.c:1140
sock_ioctl+0x4f0/0x8ac net/socket.c:1257
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #2 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}:
lock_sock_nested+0xec/0x1ec net/core/sock.c:3250
lock_sock include/net/sock.h:1668 [inline]
rfcomm_sk_state_change+0x60/0x2c8 net/bluetooth/rfcomm/sock.c:73
__rfcomm_dlc_close+0x23c/0x634 net/bluetooth/rfcomm/core.c:489
rfcomm_dlc_close+0x100/0x194 net/bluetooth/rfcomm/core.c:520
__rfcomm_sock_close+0x138/0x258 net/bluetooth/rfcomm/sock.c:220
rfcomm_sock_shutdown+0xa8/0x214 net/bluetooth/rfcomm/sock.c:912
rfcomm_sock_release+0x58/0x114 net/bluetooth/rfcomm/sock.c:933
__sock_release net/socket.c:649 [inline]
sock_close+0xb8/0x1fc net/socket.c:1336
__fput+0x30c/0x7f0 fs/file_table.c:280
____fput+0x20/0x30 fs/file_table.c:308
task_work_run+0x130/0x1e4 kernel/task_work.c:164
exit_task_work include/linux/task_work.h:32 [inline]
do_exit+0x670/0x20bc kernel/exit.c:872
do_group_exit+0x110/0x268 kernel/exit.c:994
get_signal+0x634/0x1550 kernel/signal.c:2889
do_signal arch/arm64/kernel/signal.c:890 [inline]
do_notify_resume+0x3d0/0x32b8 arch/arm64/kernel/signal.c:943
prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline]
exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline]
el0_svc+0xfc/0x1f0 arch/arm64/kernel/entry-common.c:609
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #1 (&d->lock){+.+.}-{3:3}:
__mutex_lock_common+0x194/0x2154 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0xa4/0xf8 kernel/locking/mutex.c:743
__rfcomm_dlc_close+0x200/0x634 net/bluetooth/rfcomm/core.c:487
rfcomm_dlc_close+0x100/0x194 net/bluetooth/rfcomm/core.c:520
__rfcomm_sock_close+0x138/0x258 net/bluetooth/rfcomm/sock.c:220
rfcomm_sock_shutdown+0xa8/0x214 net/bluetooth/rfcomm/sock.c:912
rfcomm_sock_release+0x58/0x114 net/bluetooth/rfcomm/sock.c:933
__sock_release net/socket.c:649 [inline]
sock_close+0xb8/0x1fc net/socket.c:1336
__fput+0x30c/0x7f0 fs/file_table.c:280
____fput+0x20/0x30 fs/file_table.c:308
task_work_run+0x130/0x1e4 kernel/task_work.c:164
exit_task_work include/linux/task_work.h:32 [inline]
do_exit+0x670/0x20bc kernel/exit.c:872
do_group_exit+0x110/0x268 kernel/exit.c:994
get_signal+0x634/0x1550 kernel/signal.c:2889
do_signal arch/arm64/kernel/signal.c:890 [inline]
do_notify_resume+0x3d0/0x32b8 arch/arm64/kernel/signal.c:943
prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline]
exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline]
el0_svc+0xfc/0x1f0 arch/arm64/kernel/entry-common.c:609
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #0 (rfcomm_mutex){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x32d4/0x7638 kernel/locking/lockdep.c:5012
lock_acquire+0x240/0x77c kernel/locking/lockdep.c:5623
__mutex_lock_common+0x194/0x2154 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0xa4/0xf8 kernel/locking/mutex.c:743
rfcomm_dlc_exists+0xb0/0x32c net/bluetooth/rfcomm/core.c:542
__rfcomm_create_dev net/bluetooth/rfcomm/tty.c:415 [inline]
rfcomm_create_dev net/bluetooth/rfcomm/tty.c:486 [inline]
rfcomm_dev_ioctl+0x938/0x2434 net/bluetooth/rfcomm/tty.c:588
rfcomm_sock_ioctl+0x98/0xf0 net/bluetooth/rfcomm/sock.c:880
sock_do_ioctl+0x134/0x2dc net/socket.c:1140
sock_ioctl+0x4f0/0x8ac net/socket.c:1257
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

other info that might help us debug this:

Chain exists of:
rfcomm_mutex --> sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM --> rfcomm_ioctl_mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(rfcomm_ioctl_mutex);
lock(sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM);
lock(rfcomm_ioctl_mutex);
lock(rfcomm_mutex);

*** DEADLOCK ***

2 locks held by syz-executor281/3988:
#0: ffff0000dd41b120 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1668 [inline]
#0: ffff0000dd41b120 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sock_ioctl+0x88/0xf0 net/bluetooth/rfcomm/sock.c:879
#1: ffff800016b9c4c8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_create_dev net/bluetooth/rfcomm/tty.c:485 [inline]
#1: ffff800016b9c4c8 (rfcomm_ioctl_mutex){+.+.}-{3:3}, at: rfcomm_dev_ioctl+0x258/0x2434 net/bluetooth/rfcomm/tty.c:588

stack backtrace:
CPU: 0 PID: 3988 Comm: syz-executor281 Not tainted 5.15.156-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call trace:
dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
dump_stack+0x1c/0x58 lib/dump_stack.c:113
print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2011
check_noncircular+0x2cc/0x378 kernel/locking/lockdep.c:2133
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x32d4/0x7638 kernel/locking/lockdep.c:5012
lock_acquire+0x240/0x77c kernel/locking/lockdep.c:5623
__mutex_lock_common+0x194/0x2154 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0xa4/0xf8 kernel/locking/mutex.c:743
rfcomm_dlc_exists+0xb0/0x32c net/bluetooth/rfcomm/core.c:542
__rfcomm_create_dev net/bluetooth/rfcomm/tty.c:415 [inline]
rfcomm_create_dev net/bluetooth/rfcomm/tty.c:486 [inline]
rfcomm_dev_ioctl+0x938/0x2434 net/bluetooth/rfcomm/tty.c:588
rfcomm_sock_ioctl+0x98/0xf0 net/bluetooth/rfcomm/sock.c:880
sock_do_ioctl+0x134/0x2dc net/socket.c:1140
sock_ioctl+0x4f0/0x8ac net/socket.c:1257
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584


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