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

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Date:   Mon, 5 Jun 2017 09:57:05 +0300
From:   Yuval Shaia <yuval.shaia@...cle.com>
To:     Jia-Ju Bai <baijiaju1990@....com>
Cc:     monis@...lanox.com, sean.hefty@...el.com, dledford@...hat.com,
        hal.rosenstock@...il.com, leon@...nel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3] rxe: Fix a sleep-in-atomic bug in post_one_send

On Thu, Jun 01, 2017 at 04:28:55PM +0800, Jia-Ju Bai wrote:
> The driver may sleep under a spin lock, and the function call path is:
> post_one_send (acquire the lock by spin_lock_irqsave)
>   init_send_wqe
>     copy_from_user --> may sleep
> 
> To fix it, the lock is released before copy_from_user, and the lock is
> acquired again after this function. The parameter "flags" is used to
> restore and save the irq status.
> Thank Leon for good advice.
> 
> This patch corrects the mistakes in V2. (Thank Ram for pointing it out)

This line should be added after "---" so it will not go into final commit
message.

> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@....com>
> ---
>  drivers/infiniband/sw/rxe/rxe_verbs.c |   13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
> index 83d709e..5293d15 100644
> --- a/drivers/infiniband/sw/rxe/rxe_verbs.c
> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
> @@ -721,11 +721,11 @@ static void init_send_wr(struct rxe_qp *qp, struct rxe_send_wr *wr,
>  
>  static int init_send_wqe(struct rxe_qp *qp, struct ib_send_wr *ibwr,
>  			 unsigned int mask, unsigned int length,
> -			 struct rxe_send_wqe *wqe)
> +			 struct rxe_send_wqe *wqe, unsigned long *flags)
>  {
>  	int num_sge = ibwr->num_sge;
>  	struct ib_sge *sge;
> -	int i;
> +	int i, err;
>  	u8 *p;
>  
>  	init_send_wr(qp, &wqe->wr, ibwr);
> @@ -740,8 +740,11 @@ static int init_send_wqe(struct rxe_qp *qp, struct ib_send_wr *ibwr,
>  
>  		sge = ibwr->sg_list;
>  		for (i = 0; i < num_sge; i++, sge++) {
> -			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;
>  
>  			else if (!qp->is_user)
> @@ -794,7 +797,7 @@ static int post_one_send(struct rxe_qp *qp, struct ib_send_wr *ibwr,
>  
>  	send_wqe = producer_addr(sq->queue);
>  
> -	err = init_send_wqe(qp, ibwr, mask, length, send_wqe);
> +	err = init_send_wqe(qp, ibwr, mask, length, send_wqe, &flags);
>  	if (unlikely(err))
>  		goto err1;
>  
> -- 
> 1.7.9.5
> 
> 
> --
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