============================================ WARNING: possible recursive locking detected 6.1.15-syzkaller #0 Not tainted -------------------------------------------- syz-executor.2/4652 is trying to acquire lock: ffff0000d66f0130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1721 [inline] ffff0000d66f0130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: l2tp_tunnel_register+0x888/0x19f8 net/l2tp/l2tp_core.c:1483 but task is already holding lock: ffff0000d66f0130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1721 [inline] ffff0000d66f0130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0x53c/0x1348 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.2/4652: #0: ffff0000d66f0130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1721 [inline] #0: ffff0000d66f0130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0x53c/0x1348 net/l2tp/l2tp_ppp.c:675 stack backtrace: CPU: 1 PID: 4652 Comm: syz-executor.2 Not tainted 6.1.15-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023 Call trace: dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165 __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106 dump_stack+0x1c/0x58 lib/dump_stack.c:113 __lock_acquire+0x6310/0x764c kernel/locking/lockdep.c:5055 lock_acquire+0x2f8/0x8dc kernel/locking/lockdep.c:5668 lock_sock_nested+0x78/0x138 net/core/sock.c:3448 lock_sock include/net/sock.h:1721 [inline] l2tp_tunnel_register+0x888/0x19f8 net/l2tp/l2tp_core.c:1483 pppol2tp_connect+0x944/0x1348 net/l2tp/l2tp_ppp.c:723 __sys_connect_file net/socket.c:1979 [inline] __sys_connect+0x268/0x290 net/socket.c:1996 __do_sys_connect net/socket.c:2006 [inline] __se_sys_connect net/socket.c:2003 [inline] __arm64_sys_connect+0x7c/0x94 net/socket.c:2003 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x64/0x218 arch/arm64/kernel/syscall.c:206 el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581