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SubjectRe: [syzbot] possible deadlock in virtual_nci_close
From
syzbot has found a reproducer for the following issue on:

HEAD commit: 1621b6eaebf7 Merge branch 'for-next/fixes' into for-kernelci
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=108bcd85880000
kernel config: https://syzkaller.appspot.com/x/.config?x=606e57fd25c5c6cc
dashboard link: https://syzkaller.appspot.com/bug?extid=8040d16d30c215f821de
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11b08dd1880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14fcee02880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/82aa7741098d/disk-1621b6ea.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f6be08c4e4c2/vmlinux-1621b6ea.xz
kernel image: https://storage.googleapis.com/syzbot-assets/296b6946258a/Image-1621b6ea.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8040d16d30c215f821de@syzkaller.appspotmail.com

nci: nci_start_poll: failed to set local general bytes
nci: __nci_request: wait_for_completion_interruptible_timeout failed 0
======================================================
WARNING: possible circular locking dependency detected
6.1.0-rc4-syzkaller-31872-g1621b6eaebf7 #0 Not tainted
------------------------------------------------------
syz-executor424/3032 is trying to acquire lock:
ffff80000d5fac10 (nci_mutex){+.+.}-{3:3}, at: virtual_nci_close+0x28/0x58 drivers/nfc/virtual_ncidev.c:44

but task is already holding lock:
ffff0000cb900350 (&ndev->req_lock){+.+.}-{3:3}, at: nci_close_device+0x74/0x2b4 net/nfc/nci/core.c:560

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&ndev->req_lock){+.+.}-{3:3}:
__mutex_lock_common+0xd4/0xca8 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
nci_request net/nfc/nci/core.c:148 [inline]
nci_set_local_general_bytes+0xbc/0x480 net/nfc/nci/core.c:774
nci_start_poll+0x1e8/0x474 net/nfc/nci/core.c:838
nfc_start_poll+0xfc/0x170 net/nfc/core.c:225
nfc_genl_start_poll+0xd4/0x174 net/nfc/netlink.c:828
genl_family_rcv_msg_doit net/netlink/genetlink.c:756 [inline]
genl_family_rcv_msg net/netlink/genetlink.c:833 [inline]
genl_rcv_msg+0x458/0x4f4 net/netlink/genetlink.c:850
netlink_rcv_skb+0xe8/0x1d4 net/netlink/af_netlink.c:2540
genl_rcv+0x38/0x50 net/netlink/genetlink.c:861
netlink_unicast_kernel+0xfc/0x1dc net/netlink/af_netlink.c:1319
netlink_unicast+0x164/0x248 net/netlink/af_netlink.c:1345
netlink_sendmsg+0x484/0x584 net/netlink/af_netlink.c:1921
sock_sendmsg_nosec net/socket.c:714 [inline]
sock_sendmsg net/socket.c:734 [inline]
____sys_sendmsg+0x2f8/0x440 net/socket.c:2482
___sys_sendmsg net/socket.c:2536 [inline]
__sys_sendmsg+0x1ac/0x228 net/socket.c:2565
__do_sys_sendmsg net/socket.c:2574 [inline]
__se_sys_sendmsg net/socket.c:2572 [inline]
__arm64_sys_sendmsg+0x2c/0x3c net/socket.c:2572
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584

-> #2 (&genl_data->genl_data_mutex){+.+.}-{3:3}:
__mutex_lock_common+0xd4/0xca8 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
nfc_urelease_event_work+0x88/0x16c net/nfc/netlink.c:1811
process_one_work+0x2d8/0x504 kernel/workqueue.c:2289
worker_thread+0x340/0x610 kernel/workqueue.c:2436
kthread+0x12c/0x158 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:863

-> #1 (nfc_devlist_mutex){+.+.}-{3:3}:
__mutex_lock_common+0xd4/0xca8 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
nfc_register_device+0x34/0x208 net/nfc/core.c:1116
nci_register_device+0x338/0x3b0 net/nfc/nci/core.c:1256
virtual_ncidev_open+0x6c/0xd8 drivers/nfc/virtual_ncidev.c:146
misc_open+0x1b8/0x200 drivers/char/misc.c:143
chrdev_open+0x2b4/0x2e8 fs/char_dev.c:414
do_dentry_open+0x364/0x748 fs/open.c:882
vfs_open+0x38/0x48 fs/open.c:1013
do_open fs/namei.c:3557 [inline]
path_openat+0xe34/0x11c4 fs/namei.c:3713
do_filp_open+0xdc/0x1b8 fs/namei.c:3740
do_sys_openat2+0xb8/0x22c fs/open.c:1310
do_sys_open fs/open.c:1326 [inline]
__do_sys_openat fs/open.c:1342 [inline]
__se_sys_openat fs/open.c:1337 [inline]
__arm64_sys_openat+0xb0/0xe0 fs/open.c:1337
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584

-> #0 (nci_mutex){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3097 [inline]
check_prevs_add kernel/locking/lockdep.c:3216 [inline]
validate_chain kernel/locking/lockdep.c:3831 [inline]
__lock_acquire+0x1530/0x3084 kernel/locking/lockdep.c:5055
lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5668
__mutex_lock_common+0xd4/0xca8 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
virtual_nci_close+0x28/0x58 drivers/nfc/virtual_ncidev.c:44
nci_close_device+0x188/0x2b4 net/nfc/nci/core.c:592
nci_unregister_device+0x3c/0x100 net/nfc/nci/core.c:1291
virtual_ncidev_close+0x70/0xb0 drivers/nfc/virtual_ncidev.c:166
__fput+0x198/0x3e4 fs/file_table.c:320
____fput+0x20/0x30 fs/file_table.c:348
task_work_run+0x100/0x148 kernel/task_work.c:179
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x2dc/0xcac kernel/exit.c:820
do_group_exit+0x98/0xcc kernel/exit.c:950
get_signal+0xabc/0xb2c kernel/signal.c:2858
do_signal+0x128/0x438 arch/arm64/kernel/signal.c:1071
do_notify_resume+0xc0/0x1f0 arch/arm64/kernel/signal.c:1124
prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
el0_svc+0x9c/0x150 arch/arm64/kernel/entry-common.c:638
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584

other info that might help us debug this:

Chain exists of:
nci_mutex --> &genl_data->genl_data_mutex --> &ndev->req_lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&ndev->req_lock);
lock(&genl_data->genl_data_mutex);
lock(&ndev->req_lock);
lock(nci_mutex);

*** DEADLOCK ***

1 lock held by syz-executor424/3032:
#0: ffff0000cb900350 (&ndev->req_lock){+.+.}-{3:3}, at: nci_close_device+0x74/0x2b4 net/nfc/nci/core.c:560

stack backtrace:
CPU: 0 PID: 3032 Comm: syz-executor424 Not tainted 6.1.0-rc4-syzkaller-31872-g1621b6eaebf7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/30/2022
Call trace:
dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:156
show_stack+0x2c/0x54 arch/arm64/kernel/stacktrace.c:163
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x104/0x16c lib/dump_stack.c:106
dump_stack+0x1c/0x58 lib/dump_stack.c:113
print_circular_bug+0x2c4/0x2c8 kernel/locking/lockdep.c:2055
check_noncircular+0x14c/0x154 kernel/locking/lockdep.c:2177
check_prev_add kernel/locking/lockdep.c:3097 [inline]
check_prevs_add kernel/locking/lockdep.c:3216 [inline]
validate_chain kernel/locking/lockdep.c:3831 [inline]
__lock_acquire+0x1530/0x3084 kernel/locking/lockdep.c:5055
lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5668
__mutex_lock_common+0xd4/0xca8 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
virtual_nci_close+0x28/0x58 drivers/nfc/virtual_ncidev.c:44
nci_close_device+0x188/0x2b4 net/nfc/nci/core.c:592
nci_unregister_device+0x3c/0x100 net/nfc/nci/core.c:1291
virtual_ncidev_close+0x70/0xb0 drivers/nfc/virtual_ncidev.c:166
__fput+0x198/0x3e4 fs/file_table.c:320
____fput+0x20/0x30 fs/file_table.c:348
task_work_run+0x100/0x148 kernel/task_work.c:179
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x2dc/0xcac kernel/exit.c:820
do_group_exit+0x98/0xcc kernel/exit.c:950
get_signal+0xabc/0xb2c kernel/signal.c:2858
do_signal+0x128/0x438 arch/arm64/kernel/signal.c:1071
do_notify_resume+0xc0/0x1f0 arch/arm64/kernel/signal.c:1124
prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
el0_svc+0x9c/0x150 arch/arm64/kernel/entry-common.c:638
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584

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