BUG: kernel NULL pointer dereference, address: 0000000000000020 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 8000000124efa067 P4D 8000000124efa067 PUD 0 Oops: Oops: 0000 [#1] SMP PTI CPU: 0 UID: 0 PID: 5170 Comm: syz.2.16 Not tainted 6.16.0-rc3-syzkaller #0 PREEMPT(undef) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 RIP: 0010:qdisc_tree_reduce_backlog+0xdc/0x180 net/sched/sch_api.c:806 Code: 48 85 c0 0f 84 88 00 00 00 49 89 c7 31 ff 44 89 ee e8 58 ca cb fe 45 85 ed 74 07 e8 0e c6 cb fe eb 3b 49 8b 47 18 4c 8b 68 08 <49> 83 7d 20 00 74 27 e8 f8 c5 cb fe 4d 8b 5d 28 4c 89 ff 44 89 e6 RSP: 0018:ffffc900019cf770 EFLAGS: 00010246 RAX: ffffffff840b7050 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff88810eee0000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000007 R10: 0000000000000000 R11: ffffffff829393a0 R12: 00000000000afff2 R13: 0000000000000000 R14: 0000000000000000 R15: ffff888124fd8400 FS: 00007fe63e70f6c0(0000) GS:ffff8882b2b07000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000020 CR3: 0000000115fe4000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: fq_codel_change+0x460/0x4f0 net/sched/sch_fq_codel.c:450 fq_codel_init+0xd6/0x290 net/sched/sch_fq_codel.c:487 qdisc_create+0x46d/0x7c0 net/sched/sch_api.c:1324 __tc_modify_qdisc net/sched/sch_api.c:-1 [inline] tc_modify_qdisc+0xb42/0xf50 net/sched/sch_api.c:1813 rtnetlink_rcv_msg+0x586/0x610 net/core/rtnetlink.c:6953 netlink_rcv_skb+0x16a/0x240 net/netlink/af_netlink.c:2534 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline] netlink_unicast+0x3bd/0x480 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x494/0x590 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg+0xc6/0xf0 net/socket.c:727 ____sys_sendmsg+0x257/0x360 net/socket.c:2566 ___sys_sendmsg+0x2de/0x320 net/socket.c:2620 __sys_sendmsg net/socket.c:2652 [inline] __do_sys_sendmsg net/socket.c:2657 [inline] __se_sys_sendmsg net/socket.c:2655 [inline] __x64_sys_sendmsg+0x110/0x1a0 net/socket.c:2655 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x8f/0x250 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fe63ec9e929 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:00007fe63e70f038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fe63eec5fa0 RCX: 00007fe63ec9e929 RDX: 0000000000000800 RSI: 0000200000000100 RDI: 0000000000000003 RBP: 00007fe63ed20b39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007fe63eec5fa0 R15: 00007ffd7f488c58 Modules linked in: CR2: 0000000000000020 ---[ end trace 0000000000000000 ]--- RIP: 0010:qdisc_tree_reduce_backlog+0xdc/0x180 net/sched/sch_api.c:806 Code: 48 85 c0 0f 84 88 00 00 00 49 89 c7 31 ff 44 89 ee e8 58 ca cb fe 45 85 ed 74 07 e8 0e c6 cb fe eb 3b 49 8b 47 18 4c 8b 68 08 <49> 83 7d 20 00 74 27 e8 f8 c5 cb fe 4d 8b 5d 28 4c 89 ff 44 89 e6 RSP: 0018:ffffc900019cf770 EFLAGS: 00010246 RAX: ffffffff840b7050 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff88810eee0000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000007 R10: 0000000000000000 R11: ffffffff829393a0 R12: 00000000000afff2 R13: 0000000000000000 R14: 0000000000000000 R15: ffff888124fd8400 FS: 00007fe63e70f6c0(0000) GS:ffff8882b2b07000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000020 CR3: 0000000115fe4000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 ---------------- Code disassembly (best guess): 0: 48 85 c0 test %rax,%rax 3: 0f 84 88 00 00 00 je 0x91 9: 49 89 c7 mov %rax,%r15 c: 31 ff xor %edi,%edi e: 44 89 ee mov %r13d,%esi 11: e8 58 ca cb fe call 0xfecbca6e 16: 45 85 ed test %r13d,%r13d 19: 74 07 je 0x22 1b: e8 0e c6 cb fe call 0xfecbc62e 20: eb 3b jmp 0x5d 22: 49 8b 47 18 mov 0x18(%r15),%rax 26: 4c 8b 68 08 mov 0x8(%rax),%r13 * 2a: 49 83 7d 20 00 cmpq $0x0,0x20(%r13) <-- trapping instruction 2f: 74 27 je 0x58 31: e8 f8 c5 cb fe call 0xfecbc62e 36: 4d 8b 5d 28 mov 0x28(%r13),%r11 3a: 4c 89 ff mov %r15,%rdi 3d: 44 89 e6 mov %r12d,%esi