syzbot


possible deadlock in pty_flush_buffer (2)

Status: upstream: reported on 2024/04/26 10:43
Subsystems: serial
[Documentation on labels]
Reported-by: syzbot+87da1f0dd6b631f8bfb9@syzkaller.appspotmail.com
First crash: 53d, last: 53d
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [serial?] possible deadlock in pty_flush_buffer (2) 0 (1) 2024/04/26 10:43
Similar bugs (1)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in pty_flush_buffer serial 1 1368d 1367d 0/27 auto-closed as invalid on 2021/01/13 17:24

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc5-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/26340 is trying to acquire lock:
ffff888062bca570 (&tty->read_wait){....}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:105 [inline]
ffff888062bca570 (&tty->read_wait){....}-{2:2}, at: __wake_up+0x1c/0x60 kernel/sched/wait.c:127

but task is already holding lock:
ffff88807e9eb4c0 (&tty->ctrl.lock){....}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:376 [inline]
ffff88807e9eb4c0 (&tty->ctrl.lock){....}-{2:2}, at: pty_flush_buffer+0xaf/0x120 drivers/tty/pty.c:213

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&tty->ctrl.lock){....}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
       __proc_set_tty+0x2c/0x6b0 drivers/tty/tty_jobctrl.c:102
       tty_open_proc_set_tty+0x1f6/0x250 drivers/tty/tty_jobctrl.c:154
       tty_open+0xdb0/0x1020 drivers/tty/tty_io.c:2184
       chrdev_open+0x26d/0x6f0 fs/char_dev.c:414
       do_dentry_open+0x8da/0x18c0 fs/open.c:955
       do_open fs/namei.c:3642 [inline]
       path_openat+0x1dfb/0x2990 fs/namei.c:3799
       do_filp_open+0x1dc/0x430 fs/namei.c:3826
       do_sys_openat2+0x17a/0x1e0 fs/open.c:1406
       do_sys_open fs/open.c:1421 [inline]
       __do_sys_openat fs/open.c:1437 [inline]
       __se_sys_openat fs/open.c:1432 [inline]
       __x64_sys_openat+0x175/0x210 fs/open.c:1432
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (&sighand->siglock){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
       __lock_task_sighand+0xc2/0x340 kernel/signal.c:1414
       lock_task_sighand include/linux/sched/signal.h:746 [inline]
       do_send_sig_info kernel/signal.c:1300 [inline]
       group_send_sig_info+0x290/0x300 kernel/signal.c:1453
       bpf_send_signal_common+0x2e8/0x3a0 kernel/trace/bpf_trace.c:881
       ____bpf_send_signal_thread kernel/trace/bpf_trace.c:898 [inline]
       bpf_send_signal_thread+0x16/0x20 kernel/trace/bpf_trace.c:896
       ___bpf_prog_run+0x3e51/0xabd0 kernel/bpf/core.c:1997
       __bpf_prog_run32+0xc1/0x100 kernel/bpf/core.c:2236
       bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
       __bpf_prog_run include/linux/filter.h:657 [inline]
       bpf_prog_run include/linux/filter.h:664 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
       bpf_trace_run4+0x176/0x460 kernel/trace/bpf_trace.c:2422
       __bpf_trace_mmap_lock_acquire_returned+0x134/0x180 include/trace/events/mmap_lock.h:52
       trace_mmap_lock_acquire_returned include/trace/events/mmap_lock.h:52 [inline]
       __mmap_lock_do_trace_acquire_returned+0x456/0x790 mm/mmap_lock.c:237
       __mmap_lock_trace_acquire_returned include/linux/mmap_lock.h:36 [inline]
       mmap_read_trylock include/linux/mmap_lock.h:166 [inline]
       get_mmap_lock_carefully mm/memory.c:5633 [inline]
       lock_mm_and_find_vma+0xeb/0x580 mm/memory.c:5693
       do_user_addr_fault+0x29c/0x1080 arch/x86/mm/fault.c:1385
       handle_page_fault arch/x86/mm/fault.c:1505 [inline]
       exc_page_fault+0x5c/0xc0 arch/x86/mm/fault.c:1563
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
       rep_movs_alternative+0x4a/0x70 arch/x86/lib/copy_user_64.S:65
       copy_user_generic arch/x86/include/asm/uaccess_64.h:110 [inline]
       raw_copy_to_user arch/x86/include/asm/uaccess_64.h:131 [inline]
       copy_to_user_iter lib/iov_iter.c:25 [inline]
       iterate_ubuf include/linux/iov_iter.h:29 [inline]
       iterate_and_advance2 include/linux/iov_iter.h:245 [inline]
       iterate_and_advance include/linux/iov_iter.h:271 [inline]
       _copy_to_iter+0x37e/0x1110 lib/iov_iter.c:185
       copy_page_to_iter lib/iov_iter.c:362 [inline]
       copy_page_to_iter+0xf1/0x180 lib/iov_iter.c:349
       pipe_read+0x543/0x1400 fs/pipe.c:327
       call_read_iter include/linux/fs.h:2104 [inline]
       new_sync_read fs/read_write.c:395 [inline]
       vfs_read+0x9fd/0xb80 fs/read_write.c:476
       ksys_read+0x1f8/0x260 fs/read_write.c:619
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (lock#10){+.+.}-{2:2}:
       local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
       __mmap_lock_do_trace_acquire_returned+0x97/0x790 mm/mmap_lock.c:237
       __mmap_lock_trace_acquire_returned include/linux/mmap_lock.h:36 [inline]
       mmap_read_trylock include/linux/mmap_lock.h:166 [inline]
       stack_map_get_build_id_offset+0x5df/0x7d0 kernel/bpf/stackmap.c:141
       __bpf_get_stack+0x6bf/0x700 kernel/bpf/stackmap.c:449
       ____bpf_get_stack_raw_tp kernel/trace/bpf_trace.c:1985 [inline]
       bpf_get_stack_raw_tp+0x124/0x160 kernel/trace/bpf_trace.c:1975
       ___bpf_prog_run+0x3e51/0xabd0 kernel/bpf/core.c:1997
       __bpf_prog_run32+0xc1/0x100 kernel/bpf/core.c:2236
       bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
       __bpf_prog_run include/linux/filter.h:657 [inline]
       bpf_prog_run include/linux/filter.h:664 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
       bpf_trace_run3+0x167/0x440 kernel/trace/bpf_trace.c:2421
       __bpf_trace_workqueue_queue_work+0x101/0x140 include/trace/events/workqueue.h:23
       trace_workqueue_queue_work include/trace/events/workqueue.h:23 [inline]
       __queue_work+0x627/0x1020 kernel/workqueue.c:2382
       queue_work_on+0xf4/0x120 kernel/workqueue.c:2435
       queue_work include/linux/workqueue.h:605 [inline]
       loop_queue_work drivers/block/loop.c:882 [inline]
       loop_queue_rq+0x5e5/0x1210 drivers/block/loop.c:1874
       __blk_mq_issue_directly+0xe0/0x270 block/blk-mq.c:2595
       blk_mq_try_issue_directly+0x1c8/0x410 block/blk-mq.c:2654
       blk_mq_submit_bio+0x18fd/0x20f0 block/blk-mq.c:3019
       __submit_bio+0xfd/0x310 block/blk-core.c:621
       __submit_bio_noacct_mq block/blk-core.c:700 [inline]
       submit_bio_noacct_nocheck+0x98a/0xd50 block/blk-core.c:729
       submit_bio_noacct+0x746/0x1ba0 block/blk-core.c:839
       submit_bh fs/buffer.c:2809 [inline]
       __bread_slow fs/buffer.c:1267 [inline]
       __bread_gfp+0x1ac/0x370 fs/buffer.c:1477
       sb_bread_unmovable include/linux/buffer_head.h:327 [inline]
       ntfs_bread+0xd9/0x210 fs/ntfs3/fsntfs.c:1025
       ntfs_read_run_nb+0x3a0/0x8f0 fs/ntfs3/fsntfs.c:1245
       ntfs_read_bh+0x3c/0xb0 fs/ntfs3/fsntfs.c:1313
       mi_read+0x1e7/0x660 fs/ntfs3/record.c:133
       ntfs_read_mft fs/ntfs3/inode.c:70 [inline]
       ntfs_iget5+0x4c2/0x3860 fs/ntfs3/inode.c:532
       ntfs_fill_super+0x22ae/0x4490 fs/ntfs3/super.c:1328
       get_tree_bdev+0x36f/0x610 fs/super.c:1614
       vfs_get_tree+0x8f/0x380 fs/super.c:1779
       do_new_mount fs/namespace.c:3352 [inline]
       path_mount+0x14e6/0x1f20 fs/namespace.c:3679
       do_mount fs/namespace.c:3692 [inline]
       __do_sys_mount fs/namespace.c:3898 [inline]
       __se_sys_mount fs/namespace.c:3875 [inline]
       __x64_sys_mount+0x297/0x320 fs/namespace.c:3875
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&pool->lock){-.-.}-{2:2}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       __queue_work+0x39e/0x1020 kernel/workqueue.c:2360
       queue_work_on+0xf4/0x120 kernel/workqueue.c:2435
       queue_work include/linux/workqueue.h:605 [inline]
       schedule_work include/linux/workqueue.h:666 [inline]
       p9_pollwake+0xc1/0x1d0 net/9p/trans_fd.c:538
       __wake_up_common+0x131/0x1e0 kernel/sched/wait.c:89
       __wake_up_common_lock kernel/sched/wait.c:106 [inline]
       __wake_up+0x31/0x60 kernel/sched/wait.c:127
       tty_set_termios+0x6db/0x9b0 drivers/tty/tty_ioctl.c:352
       set_termios+0x57e/0x7f0 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x9dc/0xd20 drivers/tty/tty_ioctl.c:826
       n_tty_ioctl_helper+0x4b/0x2b0 drivers/tty/tty_ioctl.c:986
       n_tty_ioctl+0x7f/0x370 drivers/tty/n_tty.c:2511
       tty_ioctl+0x6fa/0x1590 drivers/tty/tty_io.c:2812
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:904 [inline]
       __se_sys_ioctl fs/ioctl.c:890 [inline]
       __x64_sys_ioctl+0x193/0x220 fs/ioctl.c:890
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->read_wait){....}-{2:2}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
       lock_acquire kernel/locking/lockdep.c:5754 [inline]
       lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
       __wake_up_common_lock kernel/sched/wait.c:105 [inline]
       __wake_up+0x1c/0x60 kernel/sched/wait.c:127
       pty_flush_buffer+0xf0/0x120 drivers/tty/pty.c:215
       tty_driver_flush_buffer+0x61/0x80 drivers/tty/tty_ioctl.c:85
       tty_ldisc_hangup+0xde/0x6a0 drivers/tty/tty_ldisc.c:694
       __tty_hangup.part.0+0x426/0x8c0 drivers/tty/tty_io.c:630
       __tty_hangup drivers/tty/tty_io.c:697 [inline]
       tty_vhangup drivers/tty/tty_io.c:700 [inline]
       tty_vhangup drivers/tty/tty_io.c:697 [inline]
       tty_ioctl+0xf4e/0x1590 drivers/tty/tty_io.c:2743
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:904 [inline]
       __se_sys_ioctl fs/ioctl.c:890 [inline]
       __x64_sys_ioctl+0x193/0x220 fs/ioctl.c:890
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &tty->read_wait --> &sighand->siglock --> &tty->ctrl.lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&tty->ctrl.lock);
                               lock(&sighand->siglock);
                               lock(&tty->ctrl.lock);
  lock(&tty->read_wait);

 *** DEADLOCK ***

3 locks held by syz-executor.4/26340:
 #0: ffff88807e9eb1c0 (&tty->legacy_mutex/1){+.+.}-{3:3}, at: __tty_hangup.part.0+0xbe/0x8c0 drivers/tty/tty_io.c:590
 #1: ffff88807e9eb0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref drivers/tty/tty_ldisc.c:263 [inline]
 #1: ffff88807e9eb0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_hangup+0x30/0x6a0 drivers/tty/tty_ldisc.c:690
 #2: ffff88807e9eb4c0 (&tty->ctrl.lock){....}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:376 [inline]
 #2: ffff88807e9eb4c0 (&tty->ctrl.lock){....}-{2:2}, at: pty_flush_buffer+0xaf/0x120 drivers/tty/pty.c:213

stack backtrace:
CPU: 0 PID: 26340 Comm: syz-executor.4 Not tainted 6.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
 check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
 lock_acquire kernel/locking/lockdep.c:5754 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
 __wake_up_common_lock kernel/sched/wait.c:105 [inline]
 __wake_up+0x1c/0x60 kernel/sched/wait.c:127
 pty_flush_buffer+0xf0/0x120 drivers/tty/pty.c:215
 tty_driver_flush_buffer+0x61/0x80 drivers/tty/tty_ioctl.c:85
 tty_ldisc_hangup+0xde/0x6a0 drivers/tty/tty_ldisc.c:694
 __tty_hangup.part.0+0x426/0x8c0 drivers/tty/tty_io.c:630
 __tty_hangup drivers/tty/tty_io.c:697 [inline]
 tty_vhangup drivers/tty/tty_io.c:700 [inline]
 tty_vhangup drivers/tty/tty_io.c:697 [inline]
 tty_ioctl+0xf4e/0x1590 drivers/tty/tty_io.c:2743
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:904 [inline]
 __se_sys_ioctl fs/ioctl.c:890 [inline]
 __x64_sys_ioctl+0x193/0x220 fs/ioctl.c:890
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5d1667dea9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5d173780c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f5d167abf80 RCX: 00007f5d1667dea9
RDX: 0000000000000000 RSI: 0000000000005437 RDI: 0000000000000006
RBP: 00007f5d166ca4a4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f5d167abf80 R15: 00007ffe8e31ef58
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/04/22 10:38 upstream ed30a4a51bb1 af24b050 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root possible deadlock in pty_flush_buffer
* Struck through repros no longer work on HEAD.