linux-kernel - Re: [PATCH] infiniband: hw: qedr: add null check before pointer dereference

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Date:   Tue, 23 May 2017 10:13:49 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        Ram Amrani <ram.amrani@...ium.com>
Cc:     Doug Ledford <dledford@...hat.com>,
        Sean Hefty <sean.hefty@...el.com>,
        Hal Rosenstock <hal.rosenstock@...il.com>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] infiniband: hw: qedr: add null check before pointer
 dereference

On Mon, May 22, 2017 at 01:30:15PM -0500, Gustavo A. R. Silva wrote:
> Add null check before dereferencing pointer sgid_attr.ndev
> inside function rdma_vlan_dev_vlan_id().
>
> Addresses-Coverity-ID: 1373979
> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
> ---
>  drivers/infiniband/hw/qedr/qedr_cm.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)

+ Ram,

Ram, IB part of qedr driver doesn't exist in MAINTAINERS file.

>
> diff --git a/drivers/infiniband/hw/qedr/qedr_cm.c b/drivers/infiniband/hw/qedr/qedr_cm.c
> index 3d7705c..d86dbe8 100644
> --- a/drivers/infiniband/hw/qedr/qedr_cm.c
> +++ b/drivers/infiniband/hw/qedr/qedr_cm.c
> @@ -270,11 +270,13 @@ static inline int qedr_gsi_build_header(struct qedr_dev *dev,
>  		return rc;
>  	}
>
> -	vlan_id = rdma_vlan_dev_vlan_id(sgid_attr.ndev);
> -	if (vlan_id < VLAN_CFI_MASK)
> -		has_vlan = true;
> -	if (sgid_attr.ndev)
> +	if (sgid_attr.ndev) {
> +		vlan_id = rdma_vlan_dev_vlan_id(sgid_attr.ndev);
> +		if (vlan_id < VLAN_CFI_MASK)
> +			has_vlan = true;
> +
>  		dev_put(sgid_attr.ndev);
> +	}

I do agree that it is better than kernel panic trying to access NULL
pointer, but I'm not sure that retaining default vlan_id = 0 is correct
solution here.

>
>  	if (!memcmp(&sgid, &zgid, sizeof(sgid))) {
>  		DP_ERR(dev, "gsi post send: GID not found GID index %d\n",
> --
> 2.5.0
>

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