linux-kernel - Re: [PATCH] ublk_drv: fix NULL pointer dereference in ublk_ctrl_start

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Date: Mon, 3 Jun 2024 10:19:50 +0800
From: Li Nan <linan666@...weicloud.com>
To: Ming Lei <ming.lei@...hat.com>
Cc: axboe@...nel.dk, ZiyangZhang@...ux.alibaba.com, czhong@...hat.com,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 yukuai3@...wei.com, yi.zhang@...wei.com, houtao1@...wei.com,
 yangerkun@...wei.com
Subject: Re: [PATCH] ublk_drv: fix NULL pointer dereference in
 ublk_ctrl_start_recovery()



在 2024/6/3 8:39, Ming Lei 写道:

[...]

>> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
>> index 4e159948c912..99b621b2d40f 100644
>> --- a/drivers/block/ublk_drv.c
>> +++ b/drivers/block/ublk_drv.c
>> @@ -2630,7 +2630,8 @@ static void ublk_queue_reinit(struct ublk_device *ub, struct ublk_queue *ubq)
>>   {
>>   	int i;
>>   
>> -	WARN_ON_ONCE(!(ubq->ubq_daemon && ubq_daemon_is_dying(ubq)));
>> +	if (WARN_ON_ONCE(!(ubq->ubq_daemon && ubq_daemon_is_dying(ubq))))
>> +		return;
> 
> Yeah, it is one bug. However, it could be addressed by adding the check in
> ublk_ctrl_start_recovery() and return immediately in case of NULL ubq->ubq_daemon,
> what do you think about this way?
> 

Check ub->nr_queues_ready seems better. How about:

@@ -2662,6 +2662,8 @@ static int ublk_ctrl_start_recovery(struct 
ublk_device *ub,
         mutex_lock(&ub->mutex);
         if (!ublk_can_use_recovery(ub))
                 goto out_unlock;
+       if (!ub->nr_queues_ready)
+               goto out_unlock;
         /*
          * START_RECOVERY is only allowd after:
          *

> 
> Thanks,
> Ming

-- 
Thanks,
Nan