[v6.1] general protection fault in hfsc_qlen_notify

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syzbot

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Jul 10, 2025, 5:19:27 PM7/10/25
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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=14ee3a8c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=af043eb58258a24b
dashboard link: https://syzkaller.appspot.com/bug?extid=0fa6e6227699266e85ba
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+0fa6e6...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc000000005d: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000002e8-0x00000000000002ef]
CPU: 0 PID: 10156 Comm: syz.3.1533 Not tainted 6.1.144-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:hfsc_qlen_notify+0x2a/0x160 net/sched/sch_hfsc.c:1235
Code: 55 41 57 41 56 41 55 41 54 53 48 89 f3 49 bc 00 00 00 00 00 fc ff df e8 24 db 37 f9 4c 8d b3 ec 02 00 00 4c 89 f0 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 e3 00 00 00 41 8b 2e 31 ff 89 ee e8 5d
RSP: 0018:ffffc9000e14ee90 EFLAGS: 00010203
RAX: 000000000000005d RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc900062ea000 RSI: 0000000000000267 RDI: 0000000000000268
RBP: dffffc0000000000 R08: ffff8880548d5940 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: dffffc0000000000
R13: ffff88802a0eb000 R14: 00000000000002ec R15: ffff88802a0eb000
FS: 00007fbff1d3b6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2e719ff8 CR3: 00000000481dd000 CR4: 00000000003506f0
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: 0033:0x7fbff0f8e929
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:00007fbff1d3b038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fbff11b5fa0 RCX: 00007fbff0f8e929
RDX: 0000000000004000 RSI: 0000200000000040 RDI: 0000000000000007
RBP: 00007fbff1010b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fbff11b5fa0 R15: 00007ffd0e0e65f8
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:hfsc_qlen_notify+0x2a/0x160 net/sched/sch_hfsc.c:1235
Code: 55 41 57 41 56 41 55 41 54 53 48 89 f3 49 bc 00 00 00 00 00 fc ff df e8 24 db 37 f9 4c 8d b3 ec 02 00 00 4c 89 f0 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 e3 00 00 00 41 8b 2e 31 ff 89 ee e8 5d
RSP: 0018:ffffc9000e14ee90 EFLAGS: 00010203
RAX: 000000000000005d RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc900062ea000 RSI: 0000000000000267 RDI: 0000000000000268
RBP: dffffc0000000000 R08: ffff8880548d5940 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: dffffc0000000000
R13: ffff88802a0eb000 R14: 00000000000002ec R15: ffff88802a0eb000
FS: 00007fbff1d3b6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2e719ff8 CR3: 00000000481dd000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 55 push %rbp
1: 41 57 push %r15
3: 41 56 push %r14
5: 41 55 push %r13
7: 41 54 push %r12
9: 53 push %rbx
a: 48 89 f3 mov %rsi,%rbx
d: 49 bc 00 00 00 00 00 movabs $0xdffffc0000000000,%r12
14: fc ff df
17: e8 24 db 37 f9 call 0xf937db40
1c: 4c 8d b3 ec 02 00 00 lea 0x2ec(%rbx),%r14
23: 4c 89 f0 mov %r14,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 0f 85 e3 00 00 00 jne 0x11a
37: 41 8b 2e mov (%r14),%ebp
3a: 31 ff xor %edi,%edi
3c: 89 ee mov %ebp,%esi
3e: e8 .byte 0xe8
3f: 5d pop %rbp


---
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syzbot

unread,
Jul 14, 2025, 10:50:37 AM7/14/25
to syzkaller...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: 59a2de10b81a Linux 6.6.97
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11e9918c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=ac0b29aca872266f
dashboard link: https://syzkaller.appspot.com/bug?extid=34fa3303360b3b48eca3
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/32864b54a55c/disk-59a2de10.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b0bbe4ada642/vmlinux-59a2de10.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9e3fe91e14c2/bzImage-59a2de10.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+34fa33...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc000000005d: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000002e8-0x00000000000002ef]
CPU: 0 PID: 6427 Comm: syz.3.127 Not tainted 6.6.97-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:hfsc_qlen_notify+0x2e/0x160 net/sched/sch_hfsc.c:1237
Code: 55 41 57 41 56 41 55 41 54 53 48 89 f3 49 bc 00 00 00 00 00 fc ff df e8 d0 be f3 f8 4c 8d b3 ec 02 00 00 4c 89 f0 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 e3 00 00 00 41 8b 2e 31 ff 89 ee e8 59
RSP: 0018:ffffc9000373edd0 EFLAGS: 00010203
RAX: 000000000000005d RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc9000c9ca000 RSI: 0000000000000b1a RDI: 0000000000000b1b
RBP: dffffc0000000000 R08: ffff888028329e00 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: dffffc0000000000
R13: ffff888030ad6000 R14: 00000000000002ec R15: ffff888030ad6000
FS: 00007f9deaa8c6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c2ec027 CR3: 0000000022e74000 CR4: 00000000003506f0
Call Trace:
<TASK>
qdisc_tree_reduce_backlog+0x28b/0x470 net/sched/sch_api.c:810
hhf_change+0x817/0xd30 net/sched/sch_hhf.c:567
hhf_init+0x219/0x940 net/sched/sch_hhf.c:593
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: 0033:0x7f9de9b8e929
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:00007f9deaa8c038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f9de9db5fa0 RCX: 00007f9de9b8e929
RDX: 0000000000004000 RSI: 0000200000000280 RDI: 0000000000000003
RBP: 00007f9de9c10b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9de9db5fa0 R15: 00007ffe1f62a7d8
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:hfsc_qlen_notify+0x2e/0x160 net/sched/sch_hfsc.c:1237
Code: 55 41 57 41 56 41 55 41 54 53 48 89 f3 49 bc 00 00 00 00 00 fc ff df e8 d0 be f3 f8 4c 8d b3 ec 02 00 00 4c 89 f0 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 e3 00 00 00 41 8b 2e 31 ff 89 ee e8 59
RSP: 0018:ffffc9000373edd0 EFLAGS: 00010203
RAX: 000000000000005d RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc9000c9ca000 RSI: 0000000000000b1a RDI: 0000000000000b1b
RBP: dffffc0000000000 R08: ffff888028329e00 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: dffffc0000000000
R13: ffff888030ad6000 R14: 00000000000002ec R15: ffff888030ad6000
FS: 00007f9deaa8c6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c2ec027 CR3: 0000000022e74000 CR4: 00000000003506f0
----------------
Code disassembly (best guess):
0: 55 push %rbp
1: 41 57 push %r15
3: 41 56 push %r14
5: 41 55 push %r13
7: 41 54 push %r12
9: 53 push %rbx
a: 48 89 f3 mov %rsi,%rbx
d: 49 bc 00 00 00 00 00 movabs $0xdffffc0000000000,%r12
14: fc ff df
17: e8 d0 be f3 f8 call 0xf8f3beec
1c: 4c 8d b3 ec 02 00 00 lea 0x2ec(%rbx),%r14
23: 4c 89 f0 mov %r14,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 0f 85 e3 00 00 00 jne 0x11a
37: 41 8b 2e mov (%r14),%ebp
3a: 31 ff xor %edi,%edi
3c: 89 ee mov %ebp,%esi
3e: e8 .byte 0xe8
3f: 59 pop %rcx

syzbot

unread,
Oct 24, 2025, 5:52:18 AM10/24/25
to syzkaller...@googlegroups.com
Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.

syzbot

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Oct 25, 2025, 12:18:13 PM10/25/25
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