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From: Jason Gunthorpe <jgg@ziepe.ca>
To: Leon Romanovsky <leon@kernel.org>
Cc: Doug Ledford <dledford@redhat.com>,
	Leon Romanovsky <leonro@mellanox.com>,
	RDMA mailing list <linux-rdma@vger.kernel.org>,
	Daniel Jurgens <danielj@mellanox.com>,
	Erez Shitrit <erezsh@mellanox.com>,
	Maor Gottlieb <maorg@mellanox.com>,
	Michael Guralnik <michaelgur@mellanox.com>,
	Moni Shoua <monis@mellanox.com>,
	Parav Pandit <parav@mellanox.com>,
	Sean Hefty <sean.hefty@intel.com>,
	Valentine Fatiev <valentinef@mellanox.com>,
	Yishai Hadas <yishaih@mellanox.com>,
	Yonatan Cohen <yonatanc@mellanox.com>,
	Zhu Yanjun <yanjunz@mellanox.com>
Subject: Re: [PATCH rdma-rc 4/9] IB/ipoib: Fix double free of skb in case of multicast traffic in CM mode
Date: Thu, 13 Feb 2020 11:37:43 -0400
Message-ID: <20200213153743.GA19802@ziepe.ca> (raw)
In-Reply-To: <20200212072635.682689-5-leon@kernel.org>

On Wed, Feb 12, 2020 at 09:26:30AM +0200, Leon Romanovsky wrote:

> diff --git a/drivers/infiniband/ulp/ipoib/ipoib.h b/drivers/infiniband/ulp/ipoib/ipoib.h
> index 2aa3457a30ce..c614cb87d09b 100644
> --- a/drivers/infiniband/ulp/ipoib/ipoib.h
> +++ b/drivers/infiniband/ulp/ipoib/ipoib.h
> @@ -379,6 +379,7 @@ struct ipoib_dev_priv {
>  	struct ipoib_tx_buf *tx_ring;
>  	unsigned int	     tx_head;
>  	unsigned int	     tx_tail;
> +	atomic_t             tx_outstanding;
>  	struct ib_sge	     tx_sge[MAX_SKB_FRAGS + 1];
>  	struct ib_ud_wr      tx_wr;
>  	struct ib_wc	     send_wc[MAX_SEND_CQE];
> diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
> index c59e00a0881f..db6aace83fe5 100644
> --- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c
> +++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
> @@ -756,7 +756,7 @@ void ipoib_cm_send(struct net_device *dev, struct sk_buff *skb, struct ipoib_cm_
>  		return;
>  	}
>  
> -	if ((priv->tx_head - priv->tx_tail) == ipoib_sendq_size - 1) {
> +	if (atomic_read(&priv->tx_outstanding) == ipoib_sendq_size - 1) {
>  		ipoib_dbg(priv, "TX ring 0x%x full, stopping kernel net queue\n",
>  			  tx->qp->qp_num);
>  		netif_stop_queue(dev);
> @@ -786,7 +786,7 @@ void ipoib_cm_send(struct net_device *dev, struct sk_buff *skb, struct ipoib_cm_
>  	} else {
>  		netif_trans_update(dev);
>  		++tx->tx_head;
> -		++priv->tx_head;
> +		atomic_inc(&priv->tx_outstanding);
>  	}

This use of an atomic is very weird, probably wrong.

Why is it an atomic?  priv->tx_head wasn't an atomic, and every place
touching tx_outstanding was also touching tx_head.

I assume there is some hidden locking here? Or much more stuff is
busted up.

In that case, drop the atomic.

However, if the atomic is needed (where/why?) then something has to
be dealing with the races, and if the write side is fully locked then
an atomic is the wrong choice, use READ_ONCE/WRITE_ONCE instead

Jason

  reply index

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-12  7:26 [PATCH rdma-rc 0/9] Fixes for v5.6 Leon Romanovsky
2020-02-12  7:26 ` [PATCH rdma-rc 1/9] RDMA/ucma: Mask QPN to be 24 bits according to IBTA Leon Romanovsky
2020-02-12  7:26 ` [PATCH rdma-rc 2/9] RDMA/core: Fix protection fault in get_pkey_idx_qp_list Leon Romanovsky
2020-02-12  8:01   ` Leon Romanovsky
2020-02-12  8:06   ` Leon Romanovsky
2020-02-12  7:26 ` [PATCH rdma-rc 3/9] Revert "RDMA/cma: Simplify rdma_resolve_addr() error flow" Leon Romanovsky
2020-02-13 13:30   ` Jason Gunthorpe
2020-02-14  3:11     ` Parav Pandit
2020-02-14 14:08       ` Jason Gunthorpe
2020-02-14 14:48         ` Parav Pandit
2020-02-19 20:40   ` Jason Gunthorpe
2020-02-12  7:26 ` [PATCH rdma-rc 4/9] IB/ipoib: Fix double free of skb in case of multicast traffic in CM mode Leon Romanovsky
2020-02-13 15:37   ` Jason Gunthorpe [this message]
2020-02-13 18:10     ` Leon Romanovsky
2020-02-13 18:26       ` Jason Gunthorpe
2020-02-13 18:36         ` Leon Romanovsky
2020-02-13 19:09           ` Jason Gunthorpe
2020-02-12  7:26 ` [PATCH rdma-rc 5/9] RDMA/core: Add missing list deletion on freeing event queue Leon Romanovsky
2020-02-12  7:26 ` [PATCH rdma-rc 6/9] IB/mlx5: Fix async events cleanup flows Leon Romanovsky
2020-02-12  7:26 ` [PATCH rdma-rc 7/9] RDMA/rxe: Fix soft lockup problem due to using tasklets in softirq Leon Romanovsky
2020-02-12  7:26 ` [PATCH rdma-rc 8/9] IB/umad: Fix kernel crash while unloading ib_umad Leon Romanovsky
2020-02-13 14:28   ` Jason Gunthorpe
2020-02-13 18:03     ` Leon Romanovsky
2020-02-12  7:26 ` [PATCH rdma-rc 9/9] RDMA/mlx5: Prevent overflow in mmap offset calculations Leon Romanovsky
2020-02-13 18:03 ` [PATCH rdma-rc 0/9] Fixes for v5.6 Jason Gunthorpe

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