============================================ WARNING: possible recursive locking detected 6.2.0-syzkaller-02299-g4a7d37e824f5 #0 Not tainted -------------------------------------------- syz-executor.5/8074 is trying to acquire lock: ffff888044656130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1725 [inline] ffff888044656130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: l2tp_tunnel_register+0x1af/0xd80 net/l2tp/l2tp_core.c:1483 but task is already holding lock: ffff888044657130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1725 [inline] ffff888044657130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xadc/0x1a80 net/l2tp/l2tp_ppp.c:675 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(sk_lock-AF_PPPOX); lock(sk_lock-AF_PPPOX); *** DEADLOCK *** May be due to missing lock nesting notation 1 lock held by syz-executor.5/8074: #0: ffff888044657130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1725 [inline] #0: ffff888044657130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xadc/0x1a80 net/l2tp/l2tp_ppp.c:675 stack backtrace: CPU: 0 PID: 8074 Comm: syz-executor.5 Not tainted 6.2.0-syzkaller-02299-g4a7d37e824f5 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106 print_deadlock_bug kernel/locking/lockdep.c:2991 [inline] check_deadlock kernel/locking/lockdep.c:3034 [inline] validate_chain kernel/locking/lockdep.c:3819 [inline] __lock_acquire.cold+0x116/0x3a7 kernel/locking/lockdep.c:5056 lock_acquire kernel/locking/lockdep.c:5669 [inline] lock_acquire+0x1e3/0x660 kernel/locking/lockdep.c:5634 lock_sock_nested+0x3a/0xf0 net/core/sock.c:3471 lock_sock include/net/sock.h:1725 [inline] l2tp_tunnel_register+0x1af/0xd80 net/l2tp/l2tp_core.c:1483 pppol2tp_connect+0xcdc/0x1a80 net/l2tp/l2tp_ppp.c:723 __sys_connect_file+0x153/0x1a0 net/socket.c:1979 __sys_connect+0x165/0x1a0 net/socket.c:1996 __do_sys_connect net/socket.c:2006 [inline] __se_sys_connect net/socket.c:2003 [inline] __ia32_sys_connect+0x72/0xb0 net/socket.c:2003 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline] __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178 do_fast_syscall_32+0x33/0x70 arch/x86/entry/common.c:203 entry_SYSENTER_compat_after_hwframe+0x70/0x82 RIP: 0023:0xf7f28579 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:00000000f7f235cc EFLAGS: 00000296 ORIG_RAX: 000000000000016a RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000200000c0 RDX: 0000000000000026 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 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 retq 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