====================================================== WARNING: possible circular locking dependency detected 5.6.0-rc3-next-20200228-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.4/11430 is trying to acquire lock: ffff88808bf082a0 (&tty->termios_rwsem){++++}, at: tty_unthrottle+0x1b/0x110 drivers/tty/tty_ioctl.c:136 but task is already holding lock: ffffffff89f414c0 (sel_lock){+.+.}, at: paste_selection+0x155/0x490 drivers/tty/vt/selection.c:379 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (sel_lock){+.+.}: __mutex_lock_common kernel/locking/mutex.c:956 [inline] __mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1103 set_selection_kernel+0x38a/0x13c0 drivers/tty/vt/selection.c:222 set_selection_user+0x94/0xd7 drivers/tty/vt/selection.c:186 tioclinux+0x115/0x480 drivers/tty/vt/vt.c:3051 vt_ioctl+0x18a6/0x2450 drivers/tty/vt/vt_ioctl.c:379 tty_ioctl+0xedd/0x1440 drivers/tty/tty_io.c:2660 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x11a/0x180 fs/ioctl.c:763 __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl fs/ioctl.c:770 [inline] __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770 do_syscall_64+0xf6/0x790 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (console_lock){+.+.}: console_lock+0x44/0x80 kernel/printk/printk.c:2290 con_flush_chars drivers/tty/vt/vt.c:3224 [inline] con_flush_chars+0x35/0x90 drivers/tty/vt/vt.c:3216 n_tty_write+0xd49/0xf90 drivers/tty/n_tty.c:2350 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x48f/0x7f0 drivers/tty/tty_io.c:1046 __vfs_write+0x76/0x100 fs/read_write.c:494 vfs_write+0x262/0x5c0 fs/read_write.c:558 ksys_write+0x127/0x250 fs/read_write.c:611 do_syscall_64+0xf6/0x790 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&tty->termios_rwsem){++++}: check_prev_add kernel/locking/lockdep.c:2481 [inline] check_prevs_add kernel/locking/lockdep.c:2586 [inline] validate_chain kernel/locking/lockdep.c:3203 [inline] __lock_acquire+0x24b3/0x5270 kernel/locking/lockdep.c:4190 lock_acquire+0x197/0x420 kernel/locking/lockdep.c:4720 down_write+0x8d/0x150 kernel/locking/rwsem.c:1531 tty_unthrottle+0x1b/0x110 drivers/tty/tty_ioctl.c:136 sixpack_receive_buf drivers/net/hamradio/6pack.c:461 [inline] sixpack_receive_buf+0x810/0x1210 drivers/net/hamradio/6pack.c:435 tty_ldisc_receive_buf+0x14a/0x190 drivers/tty/tty_buffer.c:465 paste_selection+0x1e5/0x490 drivers/tty/vt/selection.c:394 tioclinux+0x12c/0x480 drivers/tty/vt/vt.c:3056 vt_ioctl+0x18a6/0x2450 drivers/tty/vt/vt_ioctl.c:379 tty_ioctl+0xedd/0x1440 drivers/tty/tty_io.c:2660 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x11a/0x180 fs/ioctl.c:763 __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl fs/ioctl.c:770 [inline] __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770 do_syscall_64+0xf6/0x790 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &tty->termios_rwsem --> console_lock --> sel_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sel_lock); lock(console_lock); lock(sel_lock); lock(&tty->termios_rwsem); *** DEADLOCK *** 3 locks held by syz-executor.4/11430: #0: ffff88808bf08090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffff8880aa1be0a8 (&buf->lock){+.+.}, at: paste_selection+0x122/0x490 drivers/tty/vt/selection.c:376 #2: ffffffff89f414c0 (sel_lock){+.+.}, at: paste_selection+0x155/0x490 drivers/tty/vt/selection.c:379 stack backtrace: CPU: 0 PID: 11430 Comm: syz-executor.4 Not tainted 5.6.0-rc3-next-20200228-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x188/0x20d lib/dump_stack.c:118 check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1812 check_prev_add kernel/locking/lockdep.c:2481 [inline] check_prevs_add kernel/locking/lockdep.c:2586 [inline] validate_chain kernel/locking/lockdep.c:3203 [inline] __lock_acquire+0x24b3/0x5270 kernel/locking/lockdep.c:4190 lock_acquire+0x197/0x420 kernel/locking/lockdep.c:4720 down_write+0x8d/0x150 kernel/locking/rwsem.c:1531 tty_unthrottle+0x1b/0x110 drivers/tty/tty_ioctl.c:136 sixpack_receive_buf drivers/net/hamradio/6pack.c:461 [inline] sixpack_receive_buf+0x810/0x1210 drivers/net/hamradio/6pack.c:435 tty_ldisc_receive_buf+0x14a/0x190 drivers/tty/tty_buffer.c:465 paste_selection+0x1e5/0x490 drivers/tty/vt/selection.c:394 tioclinux+0x12c/0x480 drivers/tty/vt/vt.c:3056 vt_ioctl+0x18a6/0x2450 drivers/tty/vt/vt_ioctl.c:379 tty_ioctl+0xedd/0x1440 drivers/tty/tty_io.c:2660 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x11a/0x180 fs/ioctl.c:763 __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl fs/ioctl.c:770 [inline] __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770 do_syscall_64+0xf6/0x790 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c849 Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f0bdb895c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f0bdb8966d4 RCX: 000000000045c849 RDX: 0000000020000040 RSI: 000000000000541c RDI: 0000000000000003 RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000056e R14: 00000000004c7ff7 R15: 000000000076bf0c