linux-kernel - Re: [PATCH V3] rxe: Fix a sleep-in-atomic bug in post_one

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Message-ID: <5935190F.7090708@163.com>
Date:   Mon, 05 Jun 2017 16:40:47 +0800
From:   Jia-Ju Bai <baijiaju1990@....com>
To:     Moni Shoua <monis@...lanox.com>
CC:     yuval.shaia@...cle.com, Sean Hefty <sean.hefty@...el.com>,
        Doug Ledford <dledford@...hat.com>,
        Hal Rosenstock <hal.rosenstock@...il.com>,
        Leon Romanovsky <leon@...nel.org>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3] rxe: Fix a sleep-in-atomic bug in post_one_send

On 06/05/2017 04:30 PM, Moni Shoua wrote:
>> -                       if (qp->is_user&&  copy_from_user(p, (__user void *)
>> -                                           (uintptr_t)sge->addr, sge->length))
>> +                       spin_unlock_irqrestore(&qp->sq.sq_lock, *flags);
>> +                       err = copy_from_user(p, (__user void *)
>> +                                       (uintptr_t)sge->addr, sge->length);
>> +                       spin_lock_irqsave(&qp->sq.sq_lock, *flags);
>> +                       if (qp->is_user&&  err)
>>                                  return -EFAULT;
> qp-_is_user is always false in this function (flow starts from
> rxe_post_send_kernel) so this line is a dead code
> In fact, this patch seems to add a serious bug when it uses
> copy_from_user() from a non user pointer.
> Do you agree?
I agree.
So, it is fine to me to remove this line, as you said in the former email:

>  Second, I think that there is no flow that leads to this function
>  when qp->is user is true so maybe the correct action is to remove this
>  line completely
>  if (qp->is_user&&  copy_from_user(p, (__user void *)