CVE-2021-47512

In the Linux kernel, the following vulnerability has been resolved:
net/sched: fq_pie: prevent dismantle issue For some reason,
fq_pie_destroy() did not copy working code from pie_destroy() and other
qdiscs, thus causing elusive bug. Before calling
del_timer_sync(&q->adapt_timer), we need to ensure timer will not rearm
itself. rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-…:
(4416 ticks this GP) idle=60d/1/0x4000000000000000 softirq=10433/10434
fqs=2579 (t=10501 jiffies g=13085 q=3989) NMI backtrace for cpu 0 CPU: 0
PID: 13 Comm: ksoftirqd/0 Not tainted 5.16.0-rc4-syzkaller #0 Hardware
name: Google Google Compute Engine/Google Compute Engine, BIOS Google
01/01/2011 Call Trace: <IRQ> __dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
nmi_cpu_backtrace.cold+0x47/0x144 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
rcu_dump_cpu_stacks+0x25e/0x3f0 kernel/rcu/tree_stall.h:343 print_cpu_stall
kernel/rcu/tree_stall.h:627 [inline] check_cpu_stall
kernel/rcu/tree_stall.h:711 [inline] rcu_pending kernel/rcu/tree.c:3878
[inline] rcu_sched_clock_irq.cold+0x9d/0x746 kernel/rcu/tree.c:2597
update_process_times+0x16d/0x200 kernel/time/timer.c:1785
tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:226
tick_sched_timer+0x1b0/0x2d0 kernel/time/tick-sched.c:1428 __run_hrtimer
kernel/time/hrtimer.c:1685 [inline] __hrtimer_run_queues+0x1c0/0xe50
kernel/time/hrtimer.c:1749 hrtimer_interrupt+0x31c/0x790
kernel/time/hrtimer.c:1811 local_apic_timer_interrupt
arch/x86/kernel/apic/apic.c:1086 [inline]
__sysvec_apic_timer_interrupt+0x146/0x530 arch/x86/kernel/apic/apic.c:1103
sysvec_apic_timer_interrupt+0x8e/0xc0 arch/x86/kernel/apic/apic.c:1097
</IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x12/0x20
arch/x86/include/asm/idtentry.h:638 RIP: 0010:write_comp_data
kernel/kcov.c:221 [inline] RIP:
0010:__sanitizer_cov_trace_const_cmp1+0x1d/0x80 kernel/kcov.c:273 Code: 54
c8 20 48 89 10 c3 66 0f 1f 44 00 00 53 41 89 fb 41 89 f1 bf 03 00 00 00 65
48 8b 0c 25 40 70 02 00 48 89 ce 4c 8b 54 24 08 <e8> 4e f7 ff ff 84 c0 74
51 48 8b 81 88 15 00 00 44 8b 81 84 15 00 RSP: 0018:ffffc90000d27b28
EFLAGS: 00000246 RAX: 0000000000000000 RBX: ffff888064bf1bf0 RCX:
ffff888011928000 RDX: ffff888011928000 RSI: ffff888011928000 RDI:
0000000000000003 RBP: ffff888064bf1c28 R08: 0000000000000000 R09:
0000000000000000 R10: ffffffff875d8295 R11: 0000000000000000 R12:
0000000000000000 R13: ffff8880783dd300 R14: 0000000000000000 R15:
0000000000000000 pie_calculate_probability+0x405/0x7c0
net/sched/sch_pie.c:418 fq_pie_timer+0x170/0x2a0 net/sched/sch_fq_pie.c:383
call_timer_fn+0x1a5/0x6b0 kernel/time/timer.c:1421 expire_timers
kernel/time/timer.c:1466 [inline] __run_timers.part.0+0x675/0xa20
kernel/time/timer.c:1734 __run_timers kernel/time/timer.c:1715 [inline]
run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1747
__do_softirq+0x29b/0x9c2 kernel/softirq.c:558 run_ksoftirqd
kernel/softirq.c:921 [inline] run_ksoftirqd+0x2d/0x60 kernel/softirq.c:913
smpboot_thread_fn+0x645/0x9c0 kernel/smpboot.c:164 kthread+0x405/0x4f0
kernel/kthread.c:327 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>