============================================ WARNING: possible recursive locking detected 6.11.0-syzkaller-11993-g3efc57369a0c #0 Not tainted -------------------------------------------- syz.1.1484/11483 is trying to acquire lock: ffffc90021ca90d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x36e/0x4b0 kernel/bpf/ringbuf.c:427 but task is already holding lock: ffffc90021c810d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x36e/0x4b0 kernel/bpf/ringbuf.c:427 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&rb->spinlock); lock(&rb->spinlock); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by syz.1.1484/11483: #0: ffffffff8ea9f7e8 (rng_mutex){+.+.}-{3:3}, at: put_rng+0x1a/0xe0 drivers/char/hw_random/core.c:141 #1: ffffffff8ddb77c0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline] #1: ffffffff8ddb77c0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #1: ffffffff8ddb77c0 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2317 [inline] #1: ffffffff8ddb77c0 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x1c2/0x590 kernel/trace/bpf_trace.c:2359 #2: ffffc90021c810d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x36e/0x4b0 kernel/bpf/ringbuf.c:427 #3: ffffffff8ddb77c0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline] #3: ffffffff8ddb77c0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #3: ffffffff8ddb77c0 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2317 [inline] #3: ffffffff8ddb77c0 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x1c2/0x590 kernel/trace/bpf_trace.c:2359 stack backtrace: CPU: 2 UID: 0 PID: 11483 Comm: syz.1.1484 Not tainted 6.11.0-syzkaller-11993-g3efc57369a0c #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_deadlock_bug+0x2e3/0x410 kernel/locking/lockdep.c:3034 check_deadlock kernel/locking/lockdep.c:3086 [inline] validate_chain kernel/locking/lockdep.c:3888 [inline] __lock_acquire+0x2185/0x3ce0 kernel/locking/lockdep.c:5199 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5822 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162 __bpf_ringbuf_reserve+0x36e/0x4b0 kernel/bpf/ringbuf.c:427 ____bpf_ringbuf_reserve kernel/bpf/ringbuf.c:478 [inline] bpf_ringbuf_reserve+0x57/0x90 kernel/bpf/ringbuf.c:470 bpf_prog_0e153dac479590bf+0x35/0x70 bpf_dispatcher_nop_func include/linux/bpf.h:1257 [inline] __bpf_prog_run include/linux/filter.h:701 [inline] bpf_prog_run include/linux/filter.h:708 [inline] __bpf_trace_run kernel/trace/bpf_trace.c:2318 [inline] bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2359 __traceiter_contention_begin+0x5a/0xa0 include/trace/events/lock.h:95 __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:94 [inline] trace_contention_begin.constprop.0+0xed/0x170 include/trace/events/lock.h:95 __pv_queued_spin_lock_slowpath+0x10b/0xc90 kernel/locking/qspinlock.c:402 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline] queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline] queued_spin_lock include/asm-generic/qspinlock.h:114 [inline] do_raw_spin_lock+0x210/0x2c0 kernel/locking/spinlock_debug.c:116 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline] _raw_spin_lock_irqsave+0x42/0x60 kernel/locking/spinlock.c:162 __bpf_ringbuf_reserve+0x36e/0x4b0 kernel/bpf/ringbuf.c:427 ____bpf_ringbuf_reserve kernel/bpf/ringbuf.c:478 [inline] bpf_ringbuf_reserve+0x57/0x90 kernel/bpf/ringbuf.c:470 bpf_prog_0e153dac479590bf+0x35/0x70 bpf_dispatcher_nop_func include/linux/bpf.h:1257 [inline] __bpf_prog_run include/linux/filter.h:701 [inline] bpf_prog_run include/linux/filter.h:708 [inline] __bpf_trace_run kernel/trace/bpf_trace.c:2318 [inline] bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2359 __traceiter_contention_begin+0x5a/0xa0 include/trace/events/lock.h:95 trace_contention_begin+0xce/0x140 include/trace/events/lock.h:95 __mutex_lock_common kernel/locking/mutex.c:610 [inline] __mutex_lock+0x182/0x9c0 kernel/locking/mutex.c:752 put_rng+0x1a/0xe0 drivers/char/hw_random/core.c:141 rng_dev_read+0x4e4/0x720 drivers/char/hw_random/core.c:248 do_loop_readv_writev fs/read_write.c:854 [inline] do_loop_readv_writev fs/read_write.c:842 [inline] vfs_readv+0x6bf/0x890 fs/read_write.c:1027 do_preadv+0x1b4/0x270 fs/read_write.c:1142 do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline] __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386 do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411 entry_SYSENTER_compat_after_hwframe+0x84/0x8e RIP: 0023:0xf741e579 Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 RSP: 002b:00000000f570656c EFLAGS: 00000296 ORIG_RAX: 000000000000014d RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000020000240 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 ---------------- Code disassembly (best guess), 2 bytes skipped: 0: 10 06 adc %al,(%rsi) 2: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi 6: 10 07 adc %al,(%rdi) 8: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi c: 10 08 adc %cl,(%rax) e: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi 1e: 00 51 52 add %dl,0x52(%rcx) 21: 55 push %rbp 22: 89 e5 mov %esp,%ebp 24: 0f 34 sysenter 26: cd 80 int $0x80 * 28: 5d pop %rbp <-- trapping instruction 29: 5a pop %rdx 2a: 59 pop %rcx 2b: c3 ret 2c: 90 nop 2d: 90 nop 2e: 90 nop 2f: 90 nop 30: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi 37: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi