Re: [PATCH RESEND] null_blk: fix null-ptr-dereference while configuring 'power' and 'submit_queues'
From: Yu Kuai
Date: Thu May 23 2024 - 03:39:21 EST
Hi,
在 2024/05/23 15:34, Zhu Yanjun 写道:
On 23.05.24 16:45, Yu Kuai wrote:
From: Yu Kuai <yukuai3@xxxxxxxxxx>
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 resuing the global mutex to protect
nullb_device_power_store() and nullb_update_nr_hw_queues() from configs.
Fixes: 45919fbfe1c4 ("null_blk: Enable modifying 'submit_queues' after
an instance has been configured")
Reported-and-tested-by: Yi Zhang <yi.zhang@xxxxxxxxxx>
Closes:
https://lore.kernel.org/all/CAHj4cs9LgsHLnjg8z06LQ3Pr5cax-+Ps+xT7AP7TPnEjStuwZA@xxxxxxxxxxxxxx/
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
drivers/block/loop.c | 2 +-
drivers/block/null_blk/main.c | 40 +++++++++++++++++++++++------------
2 files changed, 27 insertions(+), 15 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 28a95fd366fe..3e1c4f5ef714 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -2140,7 +2140,7 @@ static int loop_control_remove(int idx)
pr_warn_once("deleting an unspecified loop device is not
supported.\n");
return -EINVAL;
}
-
+
This snippet changes nothing. Can we remove it?
Of course this should be removed... it's tail space here, however,
it's not related to this patch, and I somehow merged into this patch...
Will send a v2.
Thanks,
Kuai
Zhu Yanjun
/* Hide this loop device for serialization. */
ret = mutex_lock_killable(&loop_ctl_mutex);
if (ret)
diff --git a/drivers/block/null_blk/main.c
b/drivers/block/null_blk/main.c
index 5d56ad4ce01a..eb023d267369 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -413,13 +413,25 @@ 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);
@@ -468,28 +480,31 @@ 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);
@@ -1932,15 +1947,12 @@ static int null_add_dev(struct nullb_device *dev)
nullb->q->queuedata = nullb;
blk_queue_flag_set(QUEUE_FLAG_NONROT, nullb->q);
- mutex_lock(&lock);
rv = ida_alloc(&nullb_indexes, GFP_KERNEL);
- if (rv < 0) {
- mutex_unlock(&lock);
+ if (rv < 0)
goto out_cleanup_disk;
- }
+
nullb->index = rv;
dev->index = rv;
- mutex_unlock(&lock);
if (config_item_name(&dev->group.cg_item)) {
/* Use configfs dir name as the device name */
@@ -1969,9 +1981,7 @@ static int null_add_dev(struct nullb_device *dev)
if (rv)
goto out_ida_free;
- mutex_lock(&lock);
list_add_tail(&nullb->list, &nullb_list);
- mutex_unlock(&lock);
pr_info("disk %s created\n", nullb->disk_name);
@@ -2020,7 +2030,9 @@ static int null_create_dev(void)
if (!dev)
return -ENOMEM;
+ mutex_lock(&lock);
ret = null_add_dev(dev);
+ mutex_unlock(&lock);
if (ret) {
null_free_dev(dev);
return ret;