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

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Message-ID: <20170601051220.GO5406@mtr-leonro.local>
Date:   Thu, 1 Jun 2017 08:12:20 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Jia-Ju Bai <baijiaju1990@....com>
Cc:     monis@...lanox.com, sean.hefty@...el.com, dledford@...hat.com,
        hal.rosenstock@...il.com, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rxe: Fix a sleep-in-atomic bug in post_one_send

On Thu, Jun 01, 2017 at 09:48:34AM +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.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@....com>
> ---
>  drivers/infiniband/sw/rxe/rxe_verbs.c |    9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
> index 83d709e..6fb7e1a 100644
> --- a/drivers/infiniband/sw/rxe/rxe_verbs.c
> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
> @@ -725,7 +725,7 @@ static int init_send_wqe(struct rxe_qp *qp, struct ib_send_wr *ibwr,
>  {
>  	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_irq(&qp->sq.sq_lock);

In original spin_lock, the flags of irq were saved, hence it should be
restored here too, but it is unclear to me if spin_lock is needed here
and it can't be converted to mutex_lock.

> +			err = copy_from_user(p, (__user void *)
> +					    (uintptr_t)sge->addr, sge->length);
> +			spin_lock_irq(&qp->sq.sq_lock);
> +			if (qp->is_user && err)
>  				return -EFAULT;
>
>  			else if (!qp->is_user)
> --
> 1.7.9.5
>
>
> --
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