[v6.1] general protection fault in htb_qlen_notify

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dfc486ec9cce Linux 6.1.144
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15dfda8c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=af043eb58258a24b
dashboard link: https://syzkaller.appspot.com/bug?extid=1be8ab4d23babd1c7655
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/33f04d64fdc1/disk-dfc486ec.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ae15f823ab9f/vmlinux-dfc486ec.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c42843bce2bf/bzImage-dfc486ec.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1be8ab...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000037: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000001b8-0x00000000000001bf]
CPU: 1 PID: 5155 Comm: syz.2.267 Not tainted 6.1.144-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:htb_deactivate net/sched/sch_htb.c:610 [inline]
RIP: 0010:htb_qlen_notify+0x2d/0xb0 net/sched/sch_htb.c:1486
Code: 41 56 41 55 41 54 53 49 89 f6 49 89 ff 49 bc 00 00 00 00 00 fc ff df e8 f1 a5 38 f9 49 8d 9e b8 01 00 00 49 89 dd 49 c1 ed 03 <43> 0f b6 44 25 00 84 c0 75 48 8b 2b 31 ff 89 ee e8 2e a9 38 f9 85
RSP: 0018:ffffc90003256e90 EFLAGS: 00010202
RAX: ffffffff8848319f RBX: 00000000000001b8 RCX: 0000000000080000
RDX: ffffc9000f3aa000 RSI: 0000000000000903 RDI: 0000000000000904
RBP: dffffc0000000000 R08: ffff888070fa8000 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: dffffc0000000000
R13: 0000000000000037 R14: 0000000000000000 R15: ffff88807d666000
FS: 00007fa09d1e06c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbe7276b000 CR3: 000000007bdf7000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
qdisc_tree_reduce_backlog+0x287/0x470 net/sched/sch_api.c:807
codel_change+0x970/0xdb0 net/sched/sch_codel.c:177
codel_init+0x1d4/0x3a0 net/sched/sch_codel.c:196
qdisc_create+0x7cb/0x1090 net/sched/sch_api.c:1310
tc_modify_qdisc+0xb0f/0x1be0 net/sched/sch_api.c:-1
rtnetlink_rcv_msg+0x79b/0xed0 net/core/rtnetlink.c:6153
netlink_rcv_skb+0x1de/0x420 net/netlink/af_netlink.c:2493
netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
netlink_unicast+0x74c/0x8c0 net/netlink/af_netlink.c:1337
netlink_sendmsg+0x89e/0xbc0 net/netlink/af_netlink.c:1859
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
____sys_sendmsg+0x59b/0x970 net/socket.c:2519
___sys_sendmsg+0x21c/0x290 net/socket.c:2573
__sys_sendmsg net/socket.c:2602 [inline]
__do_sys_sendmsg net/socket.c:2611 [inline]
__se_sys_sendmsg+0x19e/0x270 net/socket.c:2609
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: 0033:0x7fa09c38e929
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:00007fa09d1e0038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fa09c5b6080 RCX: 00007fa09c38e929
RDX: 000000000000c010 RSI: 0000200000000280 RDI: 0000000000000003
RBP: 00007fa09c410b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007fa09c5b6080 R15: 00007fff04449ce8
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:htb_deactivate net/sched/sch_htb.c:610 [inline]
RIP: 0010:htb_qlen_notify+0x2d/0xb0 net/sched/sch_htb.c:1486
Code: 41 56 41 55 41 54 53 49 89 f6 49 89 ff 49 bc 00 00 00 00 00 fc ff df e8 f1 a5 38 f9 49 8d 9e b8 01 00 00 49 89 dd 49 c1 ed 03 <43> 0f b6 44 25 00 84 c0 75 48 8b 2b 31 ff 89 ee e8 2e a9 38 f9 85
RSP: 0018:ffffc90003256e90 EFLAGS: 00010202

RAX: ffffffff8848319f RBX: 00000000000001b8 RCX: 0000000000080000
RDX: ffffc9000f3aa000 RSI: 0000000000000903 RDI: 0000000000000904
RBP: dffffc0000000000 R08: ffff888070fa8000 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: dffffc0000000000
R13: 0000000000000037 R14: 0000000000000000 R15: ffff88807d666000
FS: 00007fa09d1e06c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbe7276b000 CR3: 000000007bdf7000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 41 56 push %r14
2: 41 55 push %r13
4: 41 54 push %r12
6: 53 push %rbx
7: 49 89 f6 mov %rsi,%r14
a: 49 89 ff mov %rdi,%r15
d: 49 bc 00 00 00 00 00 movabs $0xdffffc0000000000,%r12
14: fc ff df
17: e8 f1 a5 38 f9 call 0xf938a60d
1c: 49 8d 9e b8 01 00 00 lea 0x1b8(%r14),%rbx
23: 49 89 dd mov %rbx,%r13
26: 49 c1 ed 03 shr $0x3,%r13
* 2a: 43 0f b6 44 25 00 movzbl 0x0(%r13,%r12,1),%eax <-- trapping instruction
30: 84 c0 test %al,%al
32: 75 48 jne 0x7c
34: 8b 2b mov (%rbx),%ebp
36: 31 ff xor %edi,%edi
38: 89 ee mov %ebp,%esi
3a: e8 2e a9 38 f9 call 0xf938a96d
3f: 85 .byte 0x85


---
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#syz undup

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2f693b607545 Linux 5.15.187
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=113fda8c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c91c2d91ea1a4388
dashboard link: https://syzkaller.appspot.com/bug?extid=a1df3cc78604c4228e1d

compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:

disk image: https://storage.googleapis.com/syzbot-assets/7769e50dbae7/disk-2f693b60.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ca8639ca4ec3/vmlinux-2f693b60.xz
kernel image: https://storage.googleapis.com/syzbot-assets/34e626fbb90f/bzImage-2f693b60.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+a1df3c...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000036: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000001b0-0x00000000000001b7]
CPU: 0 PID: 6490 Comm: syz.0.719 Not tainted 5.15.187-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025

RIP: 0010:htb_deactivate net/sched/sch_htb.c:609 [inline]
RIP: 0010:htb_qlen_notify+0x2d/0xb0 net/sched/sch_htb.c:1507
Code: 41 56 41 55 41 54 53 49 89 f6 49 89 ff 49 bc 00 00 00 00 00 fc ff df e8 c1 49 7a f9 49 8d 9e b0 01 00 00 49 89 dd 49 c1 ed 03 <43> 0f b6 44 25 00 84 c0 75 4a 8b 2b 31 ff 89 ee e8 fe 4c 7a f9 85
RSP: 0018:ffffc900033fef38 EFLAGS: 00010206
RAX: ffffffff87fd895f RBX: 00000000000001b0 RCX: 0000000000080000
RDX: ffffc90003902000 RSI: 00000000000002cf RDI: 00000000000002d0
RBP: 1ffffffff1604bb0 R08: ffff88802212bb80 R09: 0000000000000002

R10: 00000000ffffffff R11: 0000000000000002 R12: dffffc0000000000

R13: 0000000000000036 R14: 0000000000000000 R15: ffff88801f946000
FS: 00007f01c1a8a6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 000000110c3134c7 CR3: 0000000069b8b000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>

qdisc_tree_reduce_backlog+0x25f/0x430 net/sched/sch_api.c:799
codel_change+0x8d1/0xc00 net/sched/sch_codel.c:183
codel_init+0x190/0x330 net/sched/sch_codel.c:202
qdisc_create+0x7bd/0x1170 net/sched/sch_api.c:1260
tc_modify_qdisc+0xaad/0x16c0 net/sched/sch_api.c:-1
rtnetlink_rcv_msg+0x9b9/0xe60 net/core/rtnetlink.c:5650
netlink_rcv_skb+0x1e0/0x430 net/netlink/af_netlink.c:2489
netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
netlink_unicast+0x77c/0x920 net/netlink/af_netlink.c:1337
netlink_sendmsg+0x8ab/0xbc0 net/netlink/af_netlink.c:1905
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
____sys_sendmsg+0x5a2/0x8c0 net/socket.c:2436
___sys_sendmsg+0x1f0/0x260 net/socket.c:2490
__sys_sendmsg net/socket.c:2519 [inline]
__do_sys_sendmsg net/socket.c:2528 [inline]
__se_sys_sendmsg+0x190/0x250 net/socket.c:2526
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f01c3c22929

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:00007f01c1a8a038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f01c3e49fa0 RCX: 00007f01c3c22929

RDX: 000000000000c010 RSI: 0000200000000280 RDI: 0000000000000003

RBP: 00007f01c3ca4b39 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 0000000000000000 R14: 00007f01c3e49fa0 R15: 00007fff85fca9b8
</TASK>
Modules linked in:
---[ end trace ceada52d7eca228f ]---
RIP: 0010:htb_deactivate net/sched/sch_htb.c:609 [inline]
RIP: 0010:htb_qlen_notify+0x2d/0xb0 net/sched/sch_htb.c:1507
Code: 41 56 41 55 41 54 53 49 89 f6 49 89 ff 49 bc 00 00 00 00 00 fc ff df e8 c1 49 7a f9 49 8d 9e b0 01 00 00 49 89 dd 49 c1 ed 03 <43> 0f b6 44 25 00 84 c0 75 4a 8b 2b 31 ff 89 ee e8 fe 4c 7a f9 85
RSP: 0018:ffffc900033fef38 EFLAGS: 00010206

RAX: ffffffff87fd895f RBX: 00000000000001b0 RCX: 0000000000080000
RDX: ffffc90003902000 RSI: 00000000000002cf RDI: 00000000000002d0
RBP: 1ffffffff1604bb0 R08: ffff88802212bb80 R09: 0000000000000002

R10: 00000000ffffffff R11: 0000000000000002 R12: dffffc0000000000

R13: 0000000000000036 R14: 0000000000000000 R15: ffff88801f946000
FS: 00007f01c1a8a6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 000000110c3134c7 CR3: 0000000069b8b000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 41 56 push %r14
2: 41 55 push %r13
4: 41 54 push %r12
6: 53 push %rbx
7: 49 89 f6 mov %rsi,%r14
a: 49 89 ff mov %rdi,%r15
d: 49 bc 00 00 00 00 00 movabs $0xdffffc0000000000,%r12
14: fc ff df

17: e8 c1 49 7a f9 call 0xf97a49dd
1c: 49 8d 9e b0 01 00 00 lea 0x1b0(%r14),%rbx

23: 49 89 dd mov %rbx,%r13
26: 49 c1 ed 03 shr $0x3,%r13
* 2a: 43 0f b6 44 25 00 movzbl 0x0(%r13,%r12,1),%eax <-- trapping instruction
30: 84 c0 test %al,%al

32: 75 4a jne 0x7e

34: 8b 2b mov (%rbx),%ebp
36: 31 ff xor %edi,%edi
38: 89 ee mov %ebp,%esi

3a: e8 fe 4c 7a f9 call 0xf97a4d3d

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 2f693b607545 Linux 5.15.187
git tree: linux-5.15.y

console output: https://syzkaller.appspot.com/x/log.txt?x=12a3868c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=ffb429fe3ba39a3c

dashboard link: https://syzkaller.appspot.com/bug?extid=a1df3cc78604c4228e1d
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11a3868c580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16973a8c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/129cdeb1c037/disk-2f693b60.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f163e8700a20/vmlinux-2f693b60.xz
kernel image: https://storage.googleapis.com/syzbot-assets/22c8c0cbe264/Image-2f693b60.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a1df3c...@syzkaller.appspotmail.com

netlink: 4 bytes leftover after parsing attributes in process `syz.0.16'.
Unable to handle kernel paging request at virtual address dfff800000000036
Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006
CM = 0, WnR = 0
[dfff800000000036] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 4186 Comm: syz.0.16 Not tainted 5.15.187-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025

pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : htb_deactivate net/sched/sch_htb.c:609 [inline]
pc : htb_qlen_notify+0x3c/0xc8 net/sched/sch_htb.c:1507
lr : htb_qlen_notify+0x2c/0xc8 net/sched/sch_htb.c:1504
sp : ffff80001f9d6da0
x29: ffff80001f9d6da0 x28: 1ffff000025a8aa8 x27: dfff800000000000
x26: 0000000000000000 x25: ffff800012d45548 x24: 0000000000000036
x23: dfff800000000000 x22: ffff8000162edce0 x21: ffff0000d74b0000
x20: 0000000000000000 x19: 00000000000001b0 x18: 0000000000000201
x17: 0000000000000000 x16: ffff8000082bf708 x15: 00000000ffffffff
x14: 0000000000ff0100 x13: ffffffffffffffff x12: 0000000000ff0100
x11: 0000000000000201 x10: 0000000000000000 x9 : 0000000000000003
x8 : ffff0000d193d1c0 x7 : ffff80000f8d3b08 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000002
x2 : 0000000000000008 x1 : 0000000000000000 x0 : ffff0000d74b0000
Call trace:
htb_deactivate net/sched/sch_htb.c:609 [inline]
htb_qlen_notify+0x3c/0xc8 net/sched/sch_htb.c:1507
qdisc_tree_reduce_backlog+0x250/0x410 net/sched/sch_api.c:799
sfq_change net/sched/sch_sfq.c:737 [inline]
sfq_init+0x1338/0x1da4 net/sched/sch_sfq.c:801
qdisc_create+0x6e4/0xf24 net/sched/sch_api.c:1260
tc_modify_qdisc+0x8bc/0x1308 net/sched/sch_api.c:-1
rtnetlink_rcv_msg+0x9d4/0xd04 net/core/rtnetlink.c:5650
netlink_rcv_skb+0x208/0x3c4 net/netlink/af_netlink.c:2489
rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:5668
netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
netlink_unicast+0x60c/0x89c net/netlink/af_netlink.c:1337
netlink_sendmsg+0x6e8/0x9cc net/netlink/af_netlink.c:1905

sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]

____sys_sendmsg+0x61c/0x920 net/socket.c:2436
___sys_sendmsg+0x1d0/0x240 net/socket.c:2490

__sys_sendmsg net/socket.c:2519 [inline]
__do_sys_sendmsg net/socket.c:2528 [inline]

__se_sys_sendmsg net/socket.c:2526 [inline]
__arm64_sys_sendmsg+0x1a8/0x254 net/socket.c:2526
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
Code: 9106c293 d343fe78 12000a69 11000d29 (38f76b08)
---[ end trace 8309f27fdbe5c677 ]---

----------------
Code disassembly (best guess):

0: 9106c293 add x19, x20, #0x1b0
4: d343fe78 lsr x24, x19, #3
8: 12000a69 and w9, w19, #0x7
c: 11000d29 add w9, w9, #0x3
* 10: 38f76b08 ldrsb w8, [x24, x23] <-- trapping instruction


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: dfc486ec9cce Linux 6.1.144
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=14f75bd4580000

kernel config: https://syzkaller.appspot.com/x/.config?x=af043eb58258a24b
dashboard link: https://syzkaller.appspot.com/bug?extid=1be8ab4d23babd1c7655
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16b9468c580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16f8668c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/33f04d64fdc1/disk-dfc486ec.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ae15f823ab9f/vmlinux-dfc486ec.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c42843bce2bf/bzImage-dfc486ec.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1be8ab...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000037: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000001b8-0x00000000000001bf]

CPU: 1 PID: 4422 Comm: syz.0.16 Not tainted 6.1.144-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:htb_deactivate net/sched/sch_htb.c:610 [inline]
RIP: 0010:htb_qlen_notify+0x2d/0xb0 net/sched/sch_htb.c:1486
Code: 41 56 41 55 41 54 53 49 89 f6 49 89 ff 49 bc 00 00 00 00 00 fc ff df e8 f1 a5 38 f9 49 8d 9e b8 01 00 00 49 89 dd 49 c1 ed 03 <43> 0f b6 44 25 00 84 c0 75 48 8b 2b 31 ff 89 ee e8 2e a9 38 f9 85

RSP: 0018:ffffc900032d6e90 EFLAGS: 00010202
RAX: ffffffff8848319f RBX: 00000000000001b8 RCX: ffff888079391dc0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88807a750000
RBP: dffffc0000000000 R08: ffff888079391dc0 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000037 R14: 0000000000000000 R15: ffff88807a750000
FS: 0000555590528500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000200000000240 CR3: 00000000281c6000 CR4: 00000000003506e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
qdisc_tree_reduce_backlog+0x287/0x470 net/sched/sch_api.c:807
codel_change+0x970/0xdb0 net/sched/sch_codel.c:177
codel_init+0x1d4/0x3a0 net/sched/sch_codel.c:196
qdisc_create+0x7cb/0x1090 net/sched/sch_api.c:1310
tc_modify_qdisc+0xb0f/0x1be0 net/sched/sch_api.c:-1
rtnetlink_rcv_msg+0x79b/0xed0 net/core/rtnetlink.c:6153
netlink_rcv_skb+0x1de/0x420 net/netlink/af_netlink.c:2493
netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
netlink_unicast+0x74c/0x8c0 net/netlink/af_netlink.c:1337
netlink_sendmsg+0x89e/0xbc0 net/netlink/af_netlink.c:1859
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
____sys_sendmsg+0x59b/0x970 net/socket.c:2519
___sys_sendmsg+0x21c/0x290 net/socket.c:2573
__sys_sendmsg net/socket.c:2602 [inline]
__do_sys_sendmsg net/socket.c:2611 [inline]
__se_sys_sendmsg+0x19e/0x270 net/socket.c:2609
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: 0033:0x7faef638e929

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:00007ffe795e3868 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007faef65b5fa0 RCX: 00007faef638e929

RDX: 000000000000c010 RSI: 0000200000000280 RDI: 0000000000000003

RBP: 00007faef6410b39 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007faef65b5fa0 R14: 00007faef65b5fa0 R15: 0000000000000003

</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:htb_deactivate net/sched/sch_htb.c:610 [inline]
RIP: 0010:htb_qlen_notify+0x2d/0xb0 net/sched/sch_htb.c:1486
Code: 41 56 41 55 41 54 53 49 89 f6 49 89 ff 49 bc 00 00 00 00 00 fc ff df e8 f1 a5 38 f9 49 8d 9e b8 01 00 00 49 89 dd 49 c1 ed 03 <43> 0f b6 44 25 00 84 c0 75 48 8b 2b 31 ff 89 ee e8 2e a9 38 f9 85

RSP: 0018:ffffc900032d6e90 EFLAGS: 00010202
RAX: ffffffff8848319f RBX: 00000000000001b8 RCX: ffff888079391dc0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88807a750000
RBP: dffffc0000000000 R08: ffff888079391dc0 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000037 R14: 0000000000000000 R15: ffff88807a750000
FS: 0000555590528500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000200000000240 CR3: 00000000281c6000 CR4: 00000000003506e0

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9247f4e6573a Linux 6.6.98
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11fb2382580000
kernel config: https://syzkaller.appspot.com/x/.config?x=cfe840f14e117c98
dashboard link: https://syzkaller.appspot.com/bug?extid=c8853fb09659df151520

compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3855f6db0ca8/disk-9247f4e6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fe3d6afeb3a6/vmlinux-9247f4e6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7d8784621ac6/bzImage-9247f4e6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+c8853f...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000035: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000001a8-0x00000000000001af]
CPU: 1 PID: 14702 Comm: syz.3.3086 Not tainted 6.6.98-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025

RIP: 0010:htb_deactivate net/sched/sch_htb.c:613 [inline]
RIP: 0010:htb_qlen_notify+0x31/0xb0 net/sched/sch_htb.c:1489
Code: 41 56 41 55 41 54 53 49 89 f6 49 89 ff 49 bc 00 00 00 00 00 fc ff df e8 ad 90 f4 f8 49 8d 9e a8 01 00 00 49 89 dd 49 c1 ed 03 <43> 0f b6 44 25 00 84 c0 75 48 8b 2b 31 ff 89 ee e8 3a 94 f4 f8 85
RSP: 0018:ffffc90011feed90 EFLAGS: 00010206
RAX: ffffffff889115c3 RBX: 00000000000001a8 RCX: 0000000000080000
RDX: ffffc9000d2db000 RSI: 0000000000001a96 RDI: 0000000000001a97
RBP: dffffc0000000000 R08: ffff88802ea68000 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: dffffc0000000000
R13: 0000000000000035 R14: 0000000000000000 R15: ffff88805bf2c000
FS: 00007f1462fff6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000001b2d31cff8 CR3: 000000002a6e9000 CR4: 00000000003506e0
Call Trace:
<TASK>
qdisc_tree_reduce_backlog+0x28b/0x470 net/sched/sch_api.c:810
codel_change+0x974/0xdb0 net/sched/sch_codel.c:177
codel_init+0x1fd/0x3e0 net/sched/sch_codel.c:196
qdisc_create+0x8eb/0x1050 net/sched/sch_api.c:1322
tc_modify_qdisc+0xb13/0x1be0 net/sched/sch_api.c:-1
rtnetlink_rcv_msg+0x7c7/0xf10 net/core/rtnetlink.c:6475
netlink_rcv_skb+0x216/0x480 net/netlink/af_netlink.c:2537
netlink_unicast_kernel net/netlink/af_netlink.c:1323 [inline]
netlink_unicast+0x750/0x8c0 net/netlink/af_netlink.c:1349
netlink_sendmsg+0x8c1/0xbe0 net/netlink/af_netlink.c:1891
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x5bf/0x950 net/socket.c:2595
___sys_sendmsg+0x220/0x290 net/socket.c:2649
__sys_sendmsg net/socket.c:2678 [inline]
__do_sys_sendmsg net/socket.c:2687 [inline]
__se_sys_sendmsg+0x1a5/0x270 net/socket.c:2685
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f146318e929

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:00007f1462fff038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f14633b5fa0 RCX: 00007f146318e929
RDX: 0000000000004000 RSI: 0000200000000140 RDI: 0000000000000003
RBP: 00007f1463210b39 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 0000000000000000 R14: 00007f14633b5fa0 R15: 00007ffd9206c138

</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---

RIP: 0010:htb_deactivate net/sched/sch_htb.c:613 [inline]
RIP: 0010:htb_qlen_notify+0x31/0xb0 net/sched/sch_htb.c:1489
Code: 41 56 41 55 41 54 53 49 89 f6 49 89 ff 49 bc 00 00 00 00 00 fc ff df e8 ad 90 f4 f8 49 8d 9e a8 01 00 00 49 89 dd 49 c1 ed 03 <43> 0f b6 44 25 00 84 c0 75 48 8b 2b 31 ff 89 ee e8 3a 94 f4 f8 85
RSP: 0018:ffffc90011feed90 EFLAGS: 00010206
RAX: ffffffff889115c3 RBX: 00000000000001a8 RCX: 0000000000080000
RDX: ffffc9000d2db000 RSI: 0000000000001a96 RDI: 0000000000001a97
RBP: dffffc0000000000 R08: ffff88802ea68000 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: dffffc0000000000
R13: 0000000000000035 R14: 0000000000000000 R15: ffff88805bf2c000
FS: 00007f1462fff6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000001b2d31cff8 CR3: 000000002a6e9000 CR4: 00000000003506e0

----------------
Code disassembly (best guess):
0: 41 56 push %r14
2: 41 55 push %r13
4: 41 54 push %r12
6: 53 push %rbx
7: 49 89 f6 mov %rsi,%r14
a: 49 89 ff mov %rdi,%r15
d: 49 bc 00 00 00 00 00 movabs $0xdffffc0000000000,%r12
14: fc ff df

17: e8 ad 90 f4 f8 call 0xf8f490c9
1c: 49 8d 9e a8 01 00 00 lea 0x1a8(%r14),%rbx

23: 49 89 dd mov %rbx,%r13
26: 49 c1 ed 03 shr $0x3,%r13
* 2a: 43 0f b6 44 25 00 movzbl 0x0(%r13,%r12,1),%eax <-- trapping instruction
30: 84 c0 test %al,%al
32: 75 48 jne 0x7c
34: 8b 2b mov (%rbx),%ebp
36: 31 ff xor %edi,%edi
38: 89 ee mov %ebp,%esi

3a: e8 3a 94 f4 f8 call 0xf8f49479

3f: 85 .byte 0x85


---

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 23c165dde88eac405eebb59051ea1fe139a45803
Author: Victor Nogueira <vic...@mojatatu.com>
Date: Mon Jul 7 21:08:01 2025 +0000

net/sched: Abort __tc_modify_qdisc if parent class does not exist

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14488c34580000
start commit: dfc486ec9cce Linux 6.1.144
git tree: linux-6.1.y

kernel config: https://syzkaller.appspot.com/x/.config?x=af043eb58258a24b
dashboard link: https://syzkaller.appspot.com/bug?extid=1be8ab4d23babd1c7655

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16b9468c580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16f8668c580000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: net/sched: Abort __tc_modify_qdisc if parent class does not exist

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.

[syzbot]

Auto-closing this bug as obsolete.

Crashes did not happen for a while, no reproducer and no activity.