============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- syz.2.329/7421 is trying to acquire lock: ffffe8ffffd48888 ((&cell->bh_lock)){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline] ffffe8ffffd48888 ((&cell->bh_lock)){+...}-{3:3}, at: gro_cells_receive+0x404/0x790 net/core/gro_cells.c:30 but task is already holding lock: ffffe8ffffd48888 ((&cell->bh_lock)){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline] ffffe8ffffd48888 ((&cell->bh_lock)){+...}-{3:3}, at: gro_cells_receive+0x404/0x790 net/core/gro_cells.c:30 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock((&cell->bh_lock)); lock((&cell->bh_lock)); *** DEADLOCK *** May be due to missing lock nesting notation 8 locks held by syz.2.329/7421: #0: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #0: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #0: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: bpf_test_timer_enter+0x1e/0x2b0 net/bpf/test_run.c:40 #1: ffffffff8d64ab00 (local_bh){.+.+}-{1:3}, at: __local_bh_disable_ip+0xa1/0x540 kernel/softirq.c:163 #2: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: __local_bh_disable_ip+0xa1/0x540 kernel/softirq.c:163 #3: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #3: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #3: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: netif_receive_skb_list_internal+0x4fd/0xcb0 net/core/dev.c:6297 #4: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #4: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #4: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: ip6_input+0x23/0x270 net/ipv6/ip6_input.c:499 #5: ffffe8ffffd48888 ((&cell->bh_lock)){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline] #5: ffffe8ffffd48888 ((&cell->bh_lock)){+...}-{3:3}, at: gro_cells_receive+0x404/0x790 net/core/gro_cells.c:30 #6: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #6: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #6: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: ip6_input+0x23/0x270 net/ipv6/ip6_input.c:499 #7: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #7: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #7: ffffffff8d7aa4c0 (rcu_read_lock){....}-{1:3}, at: gro_cells_receive+0x50/0x790 net/core/gro_cells.c:21 stack backtrace: CPU: 1 UID: 0 PID: 7421 Comm: syz.2.329 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 Call Trace: 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 rt_spin_lock+0x88/0x3e0 kernel/locking/spinlock_rt.c:56 spin_lock include/linux/spinlock_rt.h:44 [inline] gro_cells_receive+0x404/0x790 net/core/gro_cells.c:30 ip6_tnl_rcv+0x7c/0xa0 net/ipv6/ip6_tunnel.c:903 ip6gre_rcv net/ipv6/ip6_gre.c:-1 [inline] gre_rcv+0xbfa/0x11e0 net/ipv6/ip6_gre.c:588 ip6_protocol_deliver_rcu+0xe0b/0x15c0 net/ipv6/ip6_input.c:438 ip6_input_finish+0x191/0x370 net/ipv6/ip6_input.c:489 NF_HOOK+0x30c/0x3a0 include/linux/netfilter.h:318 ip6_input+0x16a/0x270 net/ipv6/ip6_input.c:500 dst_input include/net/dst.h:474 [inline] ip6_sublist_rcv_finish+0x1c8/0x2a0 net/ipv6/ip6_input.c:88 ip6_list_rcv_finish net/ipv6/ip6_input.c:145 [inline] ip6_sublist_rcv+0xb11/0xdd0 net/ipv6/ip6_input.c:321 ipv6_list_rcv+0x3e5/0x430 net/ipv6/ip6_input.c:355 __netif_receive_skb_list_ptype net/core/dev.c:6122 [inline] __netif_receive_skb_list_core+0x5f4/0x800 net/core/dev.c:6169 __netif_receive_skb_list net/core/dev.c:6221 [inline] netif_receive_skb_list_internal+0x96f/0xcb0 net/core/dev.c:6312 netif_receive_skb_list+0x54/0x450 net/core/dev.c:6364 xdp_recv_frames net/bpf/test_run.c:280 [inline] xdp_test_run_batch net/bpf/test_run.c:361 [inline] bpf_test_run_xdp_live+0x1790/0x1b20 net/bpf/test_run.c:390 bpf_prog_test_run_xdp+0x75b/0x10e0 net/bpf/test_run.c:1331 bpf_prog_test_run+0x2cd/0x340 kernel/bpf/syscall.c:4673 __sys_bpf+0x562/0x860 kernel/bpf/syscall.c:6152 __do_sys_bpf kernel/bpf/syscall.c:6244 [inline] __se_sys_bpf kernel/bpf/syscall.c:6242 [inline] __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6242 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f3bce98efc9 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:00007f3bccbee038 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 00007f3bcebe5fa0 RCX: 00007f3bce98efc9 RDX: 0000000000000048 RSI: 0000200000000600 RDI: 000000000000000a RBP: 00007f3bcea11f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f3bcebe6038 R14: 00007f3bcebe5fa0 R15: 00007fffd6bba178