BUG: soft lockup in net_tx_action

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b172b44fcb17 Linux 4.19.206
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=178ca5b3300000
kernel config: https://syzkaller.appspot.com/x/.config?x=b9ba3521ce0be3cd
dashboard link: https://syzkaller.appspot.com/bug?extid=ac53121fd71e1d80c6b2
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ac5312...@syzkaller.appspotmail.com

Buffer I/O error on dev loop0, logical block 0, async page read
new mount options do not match the existing superblock, will be ignored
print_req_error: I/O error, dev loop0, sector 0
Buffer I/O error on dev loop0, logical block 0, async page read
watchdog: BUG: soft lockup - CPU#0 stuck for 23s! [syz-executor.5:31982]
Modules linked in:
irq event stamp: 3527883
hardirqs last enabled at (3527882): [<ffffffff81003ce4>] trace_hardirqs_on_thunk+0x1a/0x1c
hardirqs last disabled at (3527883): [<ffffffff81003d00>] trace_hardirqs_off_thunk+0x1a/0x1c
softirqs last enabled at (3462600): [<ffffffff88400678>] __do_softirq+0x678/0x980 kernel/softirq.c:318
softirqs last disabled at (3462603): [<ffffffff81393705>] invoke_softirq kernel/softirq.c:372 [inline]
softirqs last disabled at (3462603): [<ffffffff81393705>] irq_exit+0x215/0x260 kernel/softirq.c:412
CPU: 0 PID: 31982 Comm: syz-executor.5 Not tainted 4.19.206-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:fq_dequeue+0x6ff/0x12b0 net/sched/sch_fq.c:477
Code: 80 38 00 0f 84 ce fe ff ff 4c 89 f7 e8 aa af fe fa e9 c1 fe ff ff e8 b0 dc c8 fa 48 8b 44 24 10 4c 8b 7c 24 18 42 80 3c 20 00 <0f> 85 a8 09 00 00 48 8b ab 90 02 00 00 48 85 ed 0f 85 aa fe ff ff
RSP: 0018:ffff8880ba007dc8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 1ffff11011f0c322 RBX: ffff88808f861680 RCX: ffffffff8699b517
RDX: 0000000000000100 RSI: ffffffff8699b610 RDI: ffff888051ccbf58
RBP: 0000000000000000 R08: ffffffff8c664018 R09: 0000000000000000
R10: 0000000000000005 R11: ffffffff8c66401b R12: dffffc0000000000
R13: ffff88808f861918 R14: ffff88808f861900 R15: ffff88808f861910
FS: 00007fec14727700(0000) GS:ffff8880ba000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000562cff777160 CR3: 0000000097243000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
dequeue_skb net/sched/sch_generic.c:282 [inline]
qdisc_restart net/sched/sch_generic.c:385 [inline]
__qdisc_run+0x1b9/0x1640 net/sched/sch_generic.c:403
qdisc_run include/net/pkt_sched.h:120 [inline]
net_tx_action+0x4f3/0xc20 net/core/dev.c:4592
__do_softirq+0x265/0x980 kernel/softirq.c:292
invoke_softirq kernel/softirq.c:372 [inline]
irq_exit+0x215/0x260 kernel/softirq.c:412
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x136/0x550 arch/x86/kernel/apic/apic.c:1098
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894
</IRQ>
RIP: 0010:loop3+0x9/0x37d
Code: 57 18 44 89 57 18 44 03 5f 1c 44 89 5f 1c 48 3b b4 24 00 02 00 00 0f 87 eb 03 00 00 48 31 ff 66 90 45 89 cf c4 63 7b f0 ea 19 <c4> 63 7b f0 f2 0b 45 31 d7 45 31 f5 c4 63 7b f0 f2 06 41 21 d7 45
RSP: 0018:ffff888059d47300 EFLAGS: 00000283 ORIG_RAX: ffffffffffffff13
RAX: 000000005255598a RBX: 00000000f4e297a3 RCX: 000000006a6198e1
RDX: 0000000097ecc49e RSI: 0000000064e394e1 RDI: 0000000000000180
RBP: ffff888059d47600 R08: 0000000004e3f458 R09: 00000000822b0e72
R10: 00000000a7c2f973 R11: 0000000076f4ea48 R12: 0000000004e29400
R13: 00000000f6624f4b R14: 00000000ca798d2f R15: 00000000822b0e72
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60
----------------
Code disassembly (best guess):
0: 80 38 00 cmpb $0x0,(%rax)
3: 0f 84 ce fe ff ff je 0xfffffed7
9: 4c 89 f7 mov %r14,%rdi
c: e8 aa af fe fa callq 0xfafeafbb
11: e9 c1 fe ff ff jmpq 0xfffffed7
16: e8 b0 dc c8 fa callq 0xfac8dccb
1b: 48 8b 44 24 10 mov 0x10(%rsp),%rax
20: 4c 8b 7c 24 18 mov 0x18(%rsp),%r15
25: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1)
* 2a: 0f 85 a8 09 00 00 jne 0x9d8 <-- trapping instruction
30: 48 8b ab 90 02 00 00 mov 0x290(%rbx),%rbp
37: 48 85 ed test %rbp,%rbp
3a: 0f 85 aa fe ff ff jne 0xfffffeea


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.