syzbot

general protection fault, probably for non-canonical address 0xdffffc0000000004: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]
CPU: 1 PID: 1073 Comm: syz.4.166 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:qdisc_tree_reduce_backlog+0x181/0x360 net/sched/sch_api.c:803
Code: e8 44 b4 b4 fd 4d 89 ef 83 7d d0 00 74 0a e8 a6 4f 70 fd e9 a2 00 00 00 4d 8b 36 49 8d 46 20 48 89 c1 48 c1 e9 03 48 89 4d b8 <80> 3c 19 00 48 89 45 d0 74 0d 48 8b 7d d0 e8 0c b4 b4 fd 48 8b 45
RSP: 0018:ffffc90006866e68 EFLAGS: 00010202
RAX: 0000000000000020 RBX: dffffc0000000000 RCX: 0000000000000004
RDX: ffff88811726bcc0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90006866eb0 R08: ffff88811726bcc0 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: 00000000000affe0
R13: ffff888136728400 R14: 0000000000000000 R15: ffff888136728400
FS:  00007fd4ab3f56c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c32832c CR3: 00000001382cc000 CR4: 00000000003526a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 codel_change+0x8b8/0xbf0 net/sched/sch_codel.c:177
 codel_init+0x1ea/0x410 net/sched/sch_codel.c:196
 qdisc_create+0x7f3/0x1040 net/sched/sch_api.c:1311
 tc_modify_qdisc+0x8ea/0x1900 net/sched/sch_api.c:-1
 rtnetlink_rcv_msg+0x9f4/0xcf0 net/core/rtnetlink.c:6153
 netlink_rcv_skb+0x1f2/0x440 net/netlink/af_netlink.c:2503
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6171
 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline]
 netlink_unicast+0x8b1/0xa30 net/netlink/af_netlink.c:1338
 netlink_sendmsg+0x8aa/0xbc0 net/netlink/af_netlink.c:1860
 sock_sendmsg_nosec net/socket.c:716 [inline]
 __sock_sendmsg net/socket.c:728 [inline]
 ____sys_sendmsg+0x5a9/0x990 net/socket.c:2509
 ___sys_sendmsg+0x21c/0x290 net/socket.c:2563
 __sys_sendmsg net/socket.c:2592 [inline]
 __do_sys_sendmsg net/socket.c:2601 [inline]
 __se_sys_sendmsg net/socket.c:2599 [inline]
 __x64_sys_sendmsg+0x1f0/0x2c0 net/socket.c:2599
 x64_sys_call+0x171/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd4acd8ebe9
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:00007fd4ab3f5038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fd4acfc6270 RCX: 00007fd4acd8ebe9
RDX: 000000000000c010 RSI: 0000200000000280 RDI: 000000000000000a
RBP: 00007fd4ace11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd4acfc6308 R14: 00007fd4acfc6270 R15: 00007ffd361d85a8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:qdisc_tree_reduce_backlog+0x181/0x360 net/sched/sch_api.c:803
Code: e8 44 b4 b4 fd 4d 89 ef 83 7d d0 00 74 0a e8 a6 4f 70 fd e9 a2 00 00 00 4d 8b 36 49 8d 46 20 48 89 c1 48 c1 e9 03 48 89 4d b8 <80> 3c 19 00 48 89 45 d0 74 0d 48 8b 7d d0 e8 0c b4 b4 fd 48 8b 45
RSP: 0018:ffffc90006866e68 EFLAGS: 00010202
RAX: 0000000000000020 RBX: dffffc0000000000 RCX: 0000000000000004
RDX: ffff88811726bcc0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90006866eb0 R08: ffff88811726bcc0 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: 00000000000affe0
R13: ffff888136728400 R14: 0000000000000000 R15: ffff888136728400
FS:  00007fd4ab3f56c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c32832c CR3: 00000001382cc000 CR4: 00000000003526a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	e8 44 b4 b4 fd       	call   0xfdb4b449
   5:	4d 89 ef             	mov    %r13,%r15
   8:	83 7d d0 00          	cmpl   $0x0,-0x30(%rbp)
   c:	74 0a                	je     0x18
   e:	e8 a6 4f 70 fd       	call   0xfd704fb9
  13:	e9 a2 00 00 00       	jmp    0xba
  18:	4d 8b 36             	mov    (%r14),%r14
  1b:	49 8d 46 20          	lea    0x20(%r14),%rax
  1f:	48 89 c1             	mov    %rax,%rcx
  22:	48 c1 e9 03          	shr    $0x3,%rcx
  26:	48 89 4d b8          	mov    %rcx,-0x48(%rbp)
* 2a:	80 3c 19 00          	cmpb   $0x0,(%rcx,%rbx,1) <-- trapping instruction
  2e:	48 89 45 d0          	mov    %rax,-0x30(%rbp)
  32:	74 0d                	je     0x41
  34:	48 8b 7d d0          	mov    -0x30(%rbp),%rdi
  38:	e8 0c b4 b4 fd       	call   0xfdb4b449
  3d:	48                   	rex.W
  3e:	8b                   	.byte 0x8b
  3f:	45                   	rex.RB