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Message-Id: <20230610031732.2610012-1-yukuai1@huaweicloud.com>
Date: Sat, 10 Jun 2023 11:17:32 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: axboe@...nel.dk, kch@...dia.com, bvanassche@....org,
damien.lemoal@...nsource.wdc.com, vincent.fu@...sung.com,
kbusch@...nel.org
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
yukuai3@...wei.com, yukuai1@...weicloud.com, yi.zhang@...wei.com,
yangerkun@...wei.com
Subject: [PATCH -next v2] null_blk: fix null-ptr-dereference while configuring 'power' and 'submit_queues'
From: Yu Kuai <yukuai3@...wei.com>
Writing 'power' and 'submit_queues' concurrently will trigger kernel
panic:
Test script:
modprobe null_blk nr_devices=0
mkdir -p /sys/kernel/config/nullb/nullb0
while true; do echo 1 > submit_queues; echo 4 > submit_queues; done &
while true; do echo 1 > power; echo 0 > power; done
Test result:
BUG: kernel NULL pointer dereference, address: 0000000000000148
Oops: 0000 [#1] PREEMPT SMP
RIP: 0010:__lock_acquire+0x41d/0x28f0
Call Trace:
<TASK>
lock_acquire+0x121/0x450
down_write+0x5f/0x1d0
simple_recursive_removal+0x12f/0x5c0
blk_mq_debugfs_unregister_hctxs+0x7c/0x100
blk_mq_update_nr_hw_queues+0x4a3/0x720
nullb_update_nr_hw_queues+0x71/0xf0 [null_blk]
nullb_device_submit_queues_store+0x79/0xf0 [null_blk]
configfs_write_iter+0x119/0x1e0
vfs_write+0x326/0x730
ksys_write+0x74/0x150
This is because del_gendisk() can concurrent with
blk_mq_update_nr_hw_queues():
nullb_device_power_store nullb_apply_submit_queues
null_del_dev
del_gendisk
nullb_update_nr_hw_queues
if (!dev->nullb)
// still set while gendisk is deleted
return 0
blk_mq_update_nr_hw_queues
dev->nullb = NULL
Fix this problem by synchronize nullb_device_power_store() and
nullb_update_nr_hw_queues() with a mutex.
Fixes: 45919fbfe1c4 ("null_blk: Enable modifying 'submit_queues' after an instance has been configured")
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
drivers/block/null_blk/main.c | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index b3fedafe301e..16c191cb85de 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -392,13 +392,25 @@ static int nullb_update_nr_hw_queues(struct nullb_device *dev,
static int nullb_apply_submit_queues(struct nullb_device *dev,
unsigned int submit_queues)
{
- return nullb_update_nr_hw_queues(dev, submit_queues, dev->poll_queues);
+ int ret;
+
+ mutex_lock(&lock);
+ ret = nullb_update_nr_hw_queues(dev, submit_queues, dev->poll_queues);
+ mutex_unlock(&lock);
+
+ return ret;
}
static int nullb_apply_poll_queues(struct nullb_device *dev,
unsigned int poll_queues)
{
- return nullb_update_nr_hw_queues(dev, dev->submit_queues, poll_queues);
+ int ret;
+
+ mutex_lock(&lock);
+ ret = nullb_update_nr_hw_queues(dev, dev->submit_queues, poll_queues);
+ mutex_unlock(&lock);
+
+ return ret;
}
NULLB_DEVICE_ATTR(size, ulong, NULL);
@@ -444,28 +456,31 @@ static ssize_t nullb_device_power_store(struct config_item *item,
if (ret < 0)
return ret;
+ ret = count;
+ mutex_lock(&lock);
if (!dev->power && newp) {
if (test_and_set_bit(NULLB_DEV_FL_UP, &dev->flags))
- return count;
+ goto out;
+
ret = null_add_dev(dev);
if (ret) {
clear_bit(NULLB_DEV_FL_UP, &dev->flags);
- return ret;
+ goto out;
}
set_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags);
dev->power = newp;
} else if (dev->power && !newp) {
if (test_and_clear_bit(NULLB_DEV_FL_UP, &dev->flags)) {
- mutex_lock(&lock);
dev->power = newp;
null_del_dev(dev->nullb);
- mutex_unlock(&lock);
}
clear_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags);
}
- return count;
+out:
+ mutex_unlock(&lock);
+ return ret;
}
CONFIGFS_ATTR(nullb_device_, power);
--
2.39.2
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