Kernel bug: possible deadlock in down_trylock (3)
Subsystem: bpf, trace
Status: open

Crash report:
FAULT_INJECTION: forcing a failure.
name fail_usercopy, interval 1, probability 0, space 0, times 0
============================================
WARNING: possible recursive locking detected
6.16.0-next-20250731-syzkaller #0 Not tainted
--------------------------------------------
syz.3.22/6137 is trying to acquire lock:
ffffffff8e12e278 ((console_sem).lock){-...}-{2:2}, at: down_trylock+0x20/0xb0 kernel/locking/semaphore.c:176

but task is already holding lock:
ffffffff8e12e278 ((console_sem).lock){-...}-{2:2}, at: down+0x39/0xd0 kernel/locking/semaphore.c:96

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock((console_sem).lock);
  lock((console_sem).lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syz.3.22/6137:
 #0: ffffffff8e12e278 ((console_sem).lock){-...}-{2:2}, at: down+0x39/0xd0 kernel/locking/semaphore.c:96
 #1: ffffffff8e139f20 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #1: ffffffff8e139f20 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #1: ffffffff8e139f20 (rcu_read_lock){....}-{1:3}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2256 [inline]
 #1: ffffffff8e139f20 (rcu_read_lock){....}-{1:3}, at: bpf_trace_run2+0x186/0x4b0 kernel/trace/bpf_trace.c:2298

stack backtrace:
CPU: 0 UID: 0 PID: 6137 Comm: syz.3.22 Not tainted 6.16.0-next-20250731-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_deadlock_bug+0x28b/0x2a0 kernel/locking/lockdep.c:3041
 check_deadlock kernel/locking/lockdep.c:3093 [inline]
 validate_chain+0x1a3f/0x2140 kernel/locking/lockdep.c:3895
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xa7/0xf0 kernel/locking/spinlock.c:162
 down_trylock+0x20/0xb0 kernel/locking/semaphore.c:176
 __down_trylock_console_sem+0xd0/0x1e0 kernel/printk/printk.c:326
 console_trylock kernel/printk/printk.c:2868 [inline]
 console_trylock_spinning kernel/printk/printk.c:2009 [inline]
 vprintk_emit+0x320/0x7a0 kernel/printk/printk.c:2449
 _printk+0xcf/0x120 kernel/printk/printk.c:2475
 fail_dump lib/fault-inject.c:66 [inline]
 should_fail_ex+0x3f5/0x560 lib/fault-inject.c:174
 strncpy_from_user+0x36/0x290 lib/strncpy_from_user.c:118
 strncpy_from_user_nofault+0x72/0x150 mm/maccess.c:192
 bpf_trace_copy_string kernel/bpf/helpers.c:755 [inline]
 bpf_bprintf_prepare+0xbbc/0x13d0 kernel/bpf/helpers.c:976
 ____bpf_trace_printk kernel/trace/bpf_trace.c:373 [inline]
 bpf_trace_printk+0xdb/0x190 kernel/trace/bpf_trace.c:363
 bpf_prog_7c77c7e0f6645ad8+0x3e/0x44
 bpf_dispatcher_nop_func include/linux/bpf.h:1322 [inline]
 __bpf_prog_run include/linux/filter.h:718 [inline]
 bpf_prog_run include/linux/filter.h:725 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2257 [inline]
 bpf_trace_run2+0x284/0x4b0 kernel/trace/bpf_trace.c:2298
 __bpf_trace_contention_begin+0xdc/0x130 include/trace/events/lock.h:95
 __do_trace_contention_begin include/trace/events/lock.h:95 [inline]
 trace_contention_begin include/trace/events/lock.h:95 [inline]
 __down_common+0x5ad/0x6a0 kernel/locking/semaphore.c:292
 down+0x80/0xd0 kernel/locking/semaphore.c:100
 console_lock+0x145/0x1b0 kernel/printk/printk.c:2849
 do_fb_ioctl+0x509/0x750 drivers/video/fbdev/core/fb_chrdev.c:123
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f92c678eb69
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffda68c54f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f92c69b5fa0 RCX: 00007f92c678eb69
RDX: 0000200000000080 RSI: 0000000000004606 RDI: 0000000000000005
RBP: 00007ffda68c5550 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007f92c69b5fa0 R14: 00007f92c69b5fa0 R15: 0000000000000003
 </TASK>