Re: Use after free with BFQ and cgroups

["yukuai (C)" <yukuai3@huawei.com>]

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在 2021/12/22 23:21, Jan Kara 写道:
> On Thu 09-12-21 10:23:33, yukuai (C) wrote:
>> We confirmed this by our reproducer through a simple patch:
>> stop merging bfq_queues if their parents are different.
> 
> Can you please share your reproducer? I have prepared some patches which
> I'd like to verify before posting... Thanks!

Hi,

Here is the reproducer, usually the problem will come up within an
hour.

Thanks,
Kuai
> 
> 								Honza
> 

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#!/bin/bash
NR=1
basedir=/sys/fs/cgroup/blkio/null
CG_PREFIX=/sys/fs/cgroup/blkio/null/nullb

function set_cgroup()
{
	testdir=$1
	dev_id=$2
	let weight=RANDOM%900+100
	let iops=RANDOM%1000+100
	let bps=RANDOM%10485760+10485760
	echo "$weight" > $testdir/blkio.bfq.weight
	echo "$dev_id $iops" > $testdir/blkio.throttle.read_iops_device
	echo "$dev_id $iops" > $testdir/blkio.throttle.write_iops_device
	echo "$dev_id $bps" > $testdir/blkio.throttle.read_bps_device
	echo "$dev_id $bps" > $testdir/blkio.throttle.write_bps_device
}

function set_sys()
{
	local queue_dir=/sys/block/$1/queue

	let rq_affinity=RANDOM%3
	echo $rq_affinity > $queue_dir/rq_affinity

	let add_random=RANDOM%2
	echo $add_random > $queue_dir/add_random

	let rotational=RANDOM%2
	echo $rotational > $queue_dir/rotational

	let nomerges=RANDOM%2
	echo $nomerges > $queue_dir/nomerges

	let s_num=RANDOM%5
	case $s_num in
		0)
		scheduler=none
		;;
		1)
		scheduler=bfq
		;;
		2)
		scheduler=bfq
		;;
		3)
		scheduler=none
		;;
	esac
	echo bfq > $queue_dir/scheduler
}

create_cg()
{
	local i
	local path

	for i in $(seq 0 $NR)
	do
		path=${CG_PREFIX}${i}
		mkdir -p $path
	done
}

switch_cg()
{
	local path=${CG_PREFIX}$1
	local t

	for t in $(cat $path/tasks)
	do
		echo $t > /sys/fs/cgroup/blkio/tasks
	done

	echo "tasks in $path"
	cat $path/tasks
}

rm_cg()
{
	local path=${CG_PREFIX}$1

	rmdir $path
	return $?
}

mkdir $basedir
cgdir1=/sys/fs/cgroup/blkio/null/nullb0
cgdir2=/sys/fs/cgroup/blkio/null/nullb1

ADD_MOD="modprobe null_blk"
while true
do
	let flag=RANDOM%2
	if [ $flag -eq 1 ];then
		$ADD_MOD queue_mode=2 blocking=1 nr_devices=2
	else
		$ADD_MOD queue_mode=2 nr_devices=2
	fi
		
	create_cg

	dev_id=`lsblk | grep nullb0 | awk '{print $2}'`
	set_cgroup $basedir $dev_id 
	set_sys nullb0

	dev_id=`lsblk | grep nullb1 | awk '{print $2}'`
	set_cgroup $basedir $dev_id 
	set_sys nullb1

	let flag=RANDOM%20
	if [ $flag -eq 5 ];then
		echo 1 > /sys/block/nullb0/make-it-fail
		echo 1 > /sys/block/nullb1/make-it-fail
	else
		echo 0 > /sys/block/nullb0/make-it-fail
		echo 0 > /sys/block/nullb1/make-it-fail
	fi

	i=0
	while [ $i -le 3 ]
	do
		cgexec -g "blkio:null/nullb0" fio -filename=/dev/nullb0 -ioengine=libaio -time_based=1 -rw=rw -thread -size=100g -bs=512 -numjobs=4 -iodepth=8 -runtime=5 -group_reporting -name=brd-IOwrite -rwmixread=50 &>/dev/null &
		cgexec -g "blkio:null/nullb0" fio -filename=/dev/nullb0 -ioengine=psync -direct=1 -time_based=1 -rw=rw -thread -size=100g -bs=512 -numjobs=4 -iodepth=8 -runtime=5 -group_reporting -name=brd-IOwrite -rwmixread=50 &>/dev/null &
		cgexec -g "blkio:null/nullb1" fio -filename=/dev/nullb1 -ioengine=libaio -time_based=1 -rw=rw -thread -size=100g -bs=1024k -numjobs=4 -iodepth=8 -runtime=5 -group_reporting -name=brd-IOwrite -rwmixread=50 &>/dev/null &
		cgexec -g "blkio:null/nullb1" fio -filename=/dev/nullb1 -ioengine=psync -direct=1 -time_based=1 -rw=rw -thread -size=100g -bs=1024k -numjobs=4 -iodepth=8 -runtime=5 -group_reporting -name=brd-IOwrite -rwmixread=50 &>/dev/null &
		((i=i+1))
	done

	sleep 3

	until rm_cg 0
	do
		switch_cg 0
		sleep 0.1
	done

	until rm_cg 1
	do
		switch_cg 1
		sleep 0.1
	done

	while true
	do
		rmmod null_blk &>/dev/null && break
		sleep 0.1
	done
done