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Subject: Re: [PATCH] usb: musb: Get the musb_qh poniter after musb_giveback
From:   Sergey Shtylyov <s.shtylyov@omp.ru>
To:     Xingxing Luo <xingxing.luo@unisoc.com>, <b-liu@ti.com>,
        <gregkh@linuxfoundation.org>
CC:     <linux-usb@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <xingxing0070.luo@gmail.com>, <Zhiyong.Liu@unisoc.com>,
        <Cixi.Geng1@unisoc.com>, <Orson.Zhai@unisoc.com>,
        <zhang.lyra@gmail.com>
References: <20230914015656.20856-1-xingxing.luo@unisoc.com>
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Organization: Open Mobile Platform
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Date:   Thu, 14 Sep 2023 13:15:30 +0300
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On 9/14/23 1:06 PM, Sergey Shtylyov wrote:
[...]

>> When multiple threads are performing USB transmission, musb->lock will be
>> unlocked when musb_giveback is executed. At this time, qh may be released
>> in the dequeue process in other threads, resulting in a wild pointer, so
>> it needs to be here get qh again, and judge whether qh is NULL, and when
>> dequeue, you need to set qh to NULL.
>>
>> Fixes: dbac5d07d13e ("usb: musb: host: don't start next rx urb if current one failed")
>> Signed-off-by: Xingxing Luo <xingxing.luo@unisoc.com>
>> ---
>>  drivers/usb/musb/musb_host.c | 9 ++++++++-
>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
>> index a02c29216955..9df27db5847a 100644
>> --- a/drivers/usb/musb/musb_host.c
>> +++ b/drivers/usb/musb/musb_host.c
>> @@ -321,10 +321,16 @@ static void musb_advance_schedule(struct musb *musb, struct urb *urb,
>>  	musb_giveback(musb, urb, status);
>>  	qh->is_ready = ready;
>>  
>> +	/*
>> +	 * musb->lock had been unlocked in musb_giveback, so somtimes qh
> 
>    Sometimes?
> 
>> +	 * may freed, need get it again

+	 * may be freed, need to get it again

   Overlooked it in the 1st review, sorry...

[...]

MBR, Sergey