netdev - Re: [PATCH]mlx4-core: fix possible use after free in cq

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Date:	Fri, 24 Jul 2015 11:48:35 +0200
From:	Jinpu Wang <jinpu.wang@...fitbricks.com>
To:	"David S. Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Cc:	Or Gerlitz <ogerlitz@...lanox.com>,
	Jack Morgenstein <jackm@....mellanox.co.il>,
	Moni Shoua <monis@...lanox.com>,
	Yun Wang <yun.wang@...fitbricks.com>
Subject: Re: [PATCH]mlx4-core: fix possible use after free in cq_completion

On Fri, Jul 24, 2015 at 10:18 AM, Jinpu Wang
<jinpu.wang@...fitbricks.com> wrote:
> Hi all,
>
> I hit bug in OFED, I report to link below:
>
> http://marc.info/?l=linux-rdma&m=143634872328553&w=2
> I checked latest mainline Linux 4.2-rc3, it has similar bug.
> Here is the patch against Linux 4.2-rc3, compile test only.
>
> I add one copy as attachment in case mail client break the patch format.
>
> From a9fbc1ff0768acdb260e57e3324798fc0082d194 Mon Sep 17 00:00:00 2001
> From: Jack Wang <jinpu.wang@...fitbricks.com>
> Date: Thu, 23 Jul 2015 18:58:08 +0200
> Subject: [PATCH] mlx4_core: fix possible use-after-free in cq_completion
>
> It's possible during mlx4_cq_free, there are new cq_completion come,
> and there is no spin_lock protection for cq_completion, also no
> refcount protection, it will lead to use after free. So add the
> spin_lock and refcount protection in cq_completion.
>
> Signed-off-by: Jack Wang <jinpu.wang@...fitbricks.com>
> ---
>  drivers/net/ethernet/mellanox/mlx4/cq.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c
> b/drivers/net/ethernet/mellanox/mlx4/cq.c
> index 3348e64..8d7f405 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/cq.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/cq.c
> @@ -99,10 +99,15 @@ static void mlx4_add_cq_to_tasklet(struct mlx4_cq *cq)
>
>  void mlx4_cq_completion(struct mlx4_dev *dev, u32 cqn)
>  {
> +    struct mlx4_cq_table *cq_table = &mlx4_priv(dev)->cq_table;
>      struct mlx4_cq *cq;
>
> -    cq = radix_tree_lookup(&mlx4_priv(dev)->cq_table.tree,
> -                   cqn & (dev->caps.num_cqs - 1));
> +    spin_lock(&cq_table->lock);
> +    cq = radix_tree_lookup(&cq_table->tree, cqn & (dev->caps.num_cqs - 1));
> +    if (cq)
> +        atomic_inc(&cq->refcount);
> +
> +    spin_unlock(&cq_table->lock);
>      if (!cq) {
>          mlx4_dbg(dev, "Completion event for bogus CQ %08x\n", cqn);
>          return;
> @@ -111,6 +116,8 @@ void mlx4_cq_completion(struct mlx4_dev *dev, u32 cqn)
>      ++cq->arm_sn;
>
>      cq->comp(cq);
> +    if (atomic_dec_and_test(&cq->refcount))
> +        complete(&cq->free);
>  }
>
>  void mlx4_cq_event(struct mlx4_dev *dev, u32 cqn, int event_type)
> --
> 1.9.1
>

Found almost same patch as what I did, but 3 years ago :)

http://linux-rdma.vger.kernel.narkive.com/NSyWFRkW/patch-rfc-for-next-net-mlx4-core-fix-racy-flow-in-the-driver-cq-completion-handler

Could you consider to apply the patch, it fix real PANIC?

Thanks

Jack

--
Mit freundlichen Grüßen,
Best Regards,

Jack Wang

Linux Kernel Developer Storage
ProfitBricks GmbH  The IaaS-Company.

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