linux-kernel - Re: [PATCH V4] rxe: Fix a sleep-in-atomic bug in post_one

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Date:   Mon, 5 Jun 2017 13:12:49 +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, yuval.shaia@...cle.com,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4] rxe: Fix a sleep-in-atomic bug in post_one_send

On Mon, Jun 05, 2017 at 05:39:48PM +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
>
> There is no flow that makes "qp->is_user" true, and copy_from_user may
> cause bug when a non-user pointer is used. So, the line of copy_from_user
> is removed.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@....com>
> ---
> V4:
> * Remove the line of copy_from_user.
>
> V3:
> * It corrects the mistakes of remaining legacy code in V2.
>   (Thank Ram for pointing it out)
>
> V2:
> * The parameter "flags" is added to restore and save the irq status.
>   Thank Leon for good advice.
> ---
>  drivers/infiniband/sw/rxe/rxe_verbs.c |    6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
> index 83d709e..7c52c7c 100644
> --- a/drivers/infiniband/sw/rxe/rxe_verbs.c
> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
> @@ -740,11 +740,7 @@ 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))
> -				return -EFAULT;
> -
> -			else if (!qp->is_user)
> +			if (!qp->is_user)

According to the Moni's previous responses the line above is always true.

>  				memcpy(p, (void *)(uintptr_t)sge->addr,
>  				       sge->length);
>
> --
> 1.7.9.5
>
>
> --
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