Subject: Re: [syzbot] possible deadlock in virtual_nci_close

From: syzbot <[email-masked]>
Date: Mon, 14 Nov 2022 06:55:51 -0800

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: [email-masked]

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