general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 1 PID: 6952 Comm: syz.3.956 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:dequeue_head net/sched/sch_fq_codel.c:120 [inline] RIP: 0010:fq_codel_drop net/sched/sch_fq_codel.c:168 [inline] RIP: 0010:fq_codel_enqueue+0xd2d/0x1590 net/sched/sch_fq_codel.c:230 Code: 24 08 48 8b 44 24 20 80 3c 10 00 74 12 4c 89 ef e8 18 ca 88 f9 48 ba 00 00 00 00 00 fc ff df 4d 8b 65 00 4c 89 e0 48 c1 e8 03 <80> 3c 10 00 74 12 4c 89 e7 e8 f5 c9 88 f9 48 ba 00 00 00 00 00 fc RSP: 0018:ffffc90005ddf380 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 1ffff92000bbbec0 RCX: 1ffff1100a93695a RDX: dffffc0000000000 RSI: 0000000000000f7a RDI: 0000000000000f7b RBP: ffffc90005ddf4d0 R08: dffffc0000000000 R09: fffffbfff211967d R10: fffffbfff211967d R11: 1ffffffff211967c R12: 0000000000000000 R13: ffff88807e6b8000 R14: 0000000000000000 R15: 0000000000000000 FS: 00007f3a957916c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000110c33fd8b CR3: 0000000078470000 CR4: 00000000003506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: qdisc_enqueue include/net/sch_generic.h:816 [inline] netem_dequeue+0xcfc/0x13c0 net/sched/sch_netem.c:737 dequeue_skb net/sched/sch_generic.c:295 [inline] qdisc_restart net/sched/sch_generic.c:400 [inline] __qdisc_run+0x24b/0x1560 net/sched/sch_generic.c:418 __dev_xmit_skb net/core/dev.c:3970 [inline] __dev_queue_xmit+0x107e/0x3760 net/core/dev.c:4312 packet_snd net/packet/af_packet.c:3127 [inline] packet_sendmsg+0x3be8/0x4ea0 net/packet/af_packet.c:3158 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg net/socket.c:730 [inline] __sys_sendto+0x44f/0x5c0 net/socket.c:2152 __do_sys_sendto net/socket.c:2164 [inline] __se_sys_sendto net/socket.c:2160 [inline] __x64_sys_sendto+0xda/0xf0 net/socket.c:2160 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7f3a9498f749 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:00007f3a95791038 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007f3a94be5fa0 RCX: 00007f3a9498f749 RDX: 000000000000000e RSI: 0000200000000240 RDI: 0000000000000009 RBP: 00007f3a94a13f91 R08: 00002000000001c0 R09: 0000000000000014 R10: 0000000000000040 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f3a94be6038 R14: 00007f3a94be5fa0 R15: 00007ffd2de588c8 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:dequeue_head net/sched/sch_fq_codel.c:120 [inline] RIP: 0010:fq_codel_drop net/sched/sch_fq_codel.c:168 [inline] RIP: 0010:fq_codel_enqueue+0xd2d/0x1590 net/sched/sch_fq_codel.c:230 Code: 24 08 48 8b 44 24 20 80 3c 10 00 74 12 4c 89 ef e8 18 ca 88 f9 48 ba 00 00 00 00 00 fc ff df 4d 8b 65 00 4c 89 e0 48 c1 e8 03 <80> 3c 10 00 74 12 4c 89 e7 e8 f5 c9 88 f9 48 ba 00 00 00 00 00 fc RSP: 0018:ffffc90005ddf380 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 1ffff92000bbbec0 RCX: 1ffff1100a93695a RDX: dffffc0000000000 RSI: 0000000000000f7a RDI: 0000000000000f7b RBP: ffffc90005ddf4d0 R08: dffffc0000000000 R09: fffffbfff211967d R10: fffffbfff211967d R11: 1ffffffff211967c R12: 0000000000000000 R13: ffff88807e6b8000 R14: 0000000000000000 R15: 0000000000000000 FS: 00007f3a957916c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000110c33fd8b CR3: 0000000078470000 CR4: 00000000003506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 ---------------- Code disassembly (best guess): 0: 24 08 and $0x8,%al 2: 48 8b 44 24 20 mov 0x20(%rsp),%rax 7: 80 3c 10 00 cmpb $0x0,(%rax,%rdx,1) b: 74 12 je 0x1f d: 4c 89 ef mov %r13,%rdi 10: e8 18 ca 88 f9 call 0xf988ca2d 15: 48 ba 00 00 00 00 00 movabs $0xdffffc0000000000,%rdx 1c: fc ff df 1f: 4d 8b 65 00 mov 0x0(%r13),%r12 23: 4c 89 e0 mov %r12,%rax 26: 48 c1 e8 03 shr $0x3,%rax * 2a: 80 3c 10 00 cmpb $0x0,(%rax,%rdx,1) <-- trapping instruction 2e: 74 12 je 0x42 30: 4c 89 e7 mov %r12,%rdi 33: e8 f5 c9 88 f9 call 0xf988ca2d 38: 48 rex.W 39: ba 00 00 00 00 mov $0x0,%edx 3e: 00 fc add %bh,%ah