[v5.15] general protection fault in qfq_deactivate_class

[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=141ec0f0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c91c2d91ea1a4388
dashboard link: https://syzkaller.appspot.com/bug?extid=268bdb68817bd29484c2
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+268bdb...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 0 PID: 7523 Comm: syz.0.965 Not tainted 5.15.187-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:qfq_deactivate_class+0x2e/0x1290 net/sched/sch_qfq.c:354
Code: 56 41 55 41 54 53 48 83 ec 60 49 89 f6 49 89 fd 48 bd 00 00 00 00 00 fc ff df e8 1d 51 73 f9 49 8d 7e 68 48 89 f8 48 c1 e8 03 <80> 3c 28 00 74 05 e8 07 ca b8 f9 49 8b 5e 68 4d 8d 7e 58 4c 89 ff
RSP: 0018:ffffc900030eeed8 EFLAGS: 00010202
RAX: 000000000000000d RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc90015402000 RSI: 00000000000002cb RDI: 0000000000000068
RBP: dffffc0000000000 R08: ffff88802b519dc0 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: ffff888061dc0000
R13: ffff888061dc02c0 R14: 0000000000000000 R15: ffffffff8b02b120
FS: 00007fb9d70aa6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb9d92df394 CR3: 0000000061d16000 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: 0033:0x7fb9d9242929
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:00007fb9d70aa038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fb9d9469fa0 RCX: 00007fb9d9242929
RDX: 000000000000c010 RSI: 0000200000000280 RDI: 0000000000000003
RBP: 00007fb9d92c4b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fb9d9469fa0 R15: 00007fff8a4bdcf8
</TASK>
Modules linked in:
---[ end trace d6b6b27b31db5c5f ]---
RIP: 0010:qfq_deactivate_class+0x2e/0x1290 net/sched/sch_qfq.c:354
Code: 56 41 55 41 54 53 48 83 ec 60 49 89 f6 49 89 fd 48 bd 00 00 00 00 00 fc ff df e8 1d 51 73 f9 49 8d 7e 68 48 89 f8 48 c1 e8 03 <80> 3c 28 00 74 05 e8 07 ca b8 f9 49 8b 5e 68 4d 8d 7e 58 4c 89 ff
RSP: 0018:ffffc900030eeed8 EFLAGS: 00010202
RAX: 000000000000000d RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc90015402000 RSI: 00000000000002cb RDI: 0000000000000068
RBP: dffffc0000000000 R08: ffff88802b519dc0 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: ffff888061dc0000
R13: ffff888061dc02c0 R14: 0000000000000000 R15: ffffffff8b02b120
FS: 00007fb9d70aa6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb9d92df394 CR3: 0000000061d16000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 56 push %rsi
1: 41 55 push %r13
3: 41 54 push %r12
5: 53 push %rbx
6: 48 83 ec 60 sub $0x60,%rsp
a: 49 89 f6 mov %rsi,%r14
d: 49 89 fd mov %rdi,%r13
10: 48 bd 00 00 00 00 00 movabs $0xdffffc0000000000,%rbp
17: fc ff df
1a: e8 1d 51 73 f9 call 0xf973513c
1f: 49 8d 7e 68 lea 0x68(%r14),%rdi
23: 48 89 f8 mov %rdi,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 80 3c 28 00 cmpb $0x0,(%rax,%rbp,1) <-- trapping instruction
2e: 74 05 je 0x35
30: e8 07 ca b8 f9 call 0xf9b8ca3c
35: 49 8b 5e 68 mov 0x68(%r14),%rbx
39: 4d 8d 7e 58 lea 0x58(%r14),%r15
3d: 4c 89 ff mov %r15,%rdi


---
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[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=151b3a8c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=ffb429fe3ba39a3c

dashboard link: https://syzkaller.appspot.com/bug?extid=268bdb68817bd29484c2
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=10ed0d82580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=169620f0580000

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+268bdb...@syzkaller.appspotmail.com

Unable to handle kernel paging request at virtual address dfff80000000000d
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
[dfff80000000000d] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 4164 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 : qfq_deactivate_class+0x40/0xf5c net/sched/sch_qfq.c:354
lr : qfq_deactivate_class+0x38/0xf5c net/sched/sch_qfq.c:353
sp : ffff80001fc16c80
x29: ffff80001fc16cc0 x28: 1ffff000025a9424 x27: ffff0000ceb9c2c0
x26: dfff800000000000 x25: ffff800012d4a128 x24: ffff800012d4a120
x23: 0000000000000000 x22: ffff8000162edce0 x21: ffff0000ceb9c000
x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000201
x17: 0000000000000000 x16: ffff8000082bf708 x15: 00000000ffffffff
x14: 0000000000ff0100 x13: ffffffffffffffff x12: 0000000000ff0100
x11: 0000000000000201 x10: 0000000000000000 x9 : ffff80000f9a82f0
x8 : 000000000000000d x7 : ffff80000f8d3b08 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000002
x2 : 0000000000000008 x1 : 0000000000000000 x0 : 0000000000000068
Call trace:
qfq_deactivate_class+0x40/0xf5c net/sched/sch_qfq.c:354
qfq_qlen_notify+0x28/0x38 net/sched/sch_qfq.c:1431
qdisc_tree_reduce_backlog+0x250/0x410 net/sched/sch_api.c:799
codel_change+0x70c/0x9f8 net/sched/sch_codel.c:183
codel_init+0x14c/0x2f0 net/sched/sch_codel.c:202
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: f2fbfffa 962b47df 9101a280 d343fc08 (387a6908)
---[ end trace 00367777c04a9909 ]---

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

0: f2fbfffa movk x26, #0xdfff, lsl #48
4: 962b47df bl 0xfffffffff8ad1f80
8: 9101a280 add x0, x20, #0x68
c: d343fc08 lsr x8, x0, #3
* 10: 387a6908 ldrb w8, [x8, x26] <-- trapping instruction


---
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[syzbot]

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