netdev - Re: [PATCH v4 net-next] vmxnet3: Remove buf_info from device accessible structures

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Message-ID: <20210127161017.2d9adf4a@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 27 Jan 2021 16:10:17 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Ronak Doshi <doshir@...are.com>
Cc:     <netdev@...r.kernel.org>, Petr Vandrovec <petr@...are.com>,
        "maintainer:VMWARE VMXNET3 ETHERNET DRIVER" <pv-drivers@...are.com>,
        "David S. Miller" <davem@...emloft.net>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 net-next] vmxnet3: Remove buf_info from device
 accessible structures

On Tue, 26 Jan 2021 11:06:40 -0800 Ronak Doshi wrote:
> buf_info structures in RX & TX queues are private driver data that
> do not need to be visible to the device.  Although there is physical
> address and length in the queue descriptor that points to these
> structures, their layout is not standardized, and device never looks
> at them.
> 
> So lets allocate these structures in non-DMA-able memory, and fill
> physical address as all-ones and length as zero in the queue
> descriptor.
> 
> That should alleviate worries brought by Martin Radev in
> https://lists.osuosl.org/pipermail/intel-wired-lan/Week-of-Mon-20210104/022829.html
> that malicious vmxnet3 device could subvert SVM/TDX guarantees.
> 
> Signed-off-by: Petr Vandrovec <petr@...are.com>
> Signed-off-by: Ronak Doshi <doshir@...are.com>

Checkpatch says:

WARNING: kfree(NULL) is safe and this check is probably not required
#39: FILE: drivers/net/vmxnet3/vmxnet3_drv.c:455:
 	if (tq->buf_info) {
+		kfree(tq->buf_info);

WARNING: kfree(NULL) is safe and this check is probably not required
#73: FILE: drivers/net/vmxnet3/vmxnet3_drv.c:1737:
 	if (rq->buf_info[0]) {
+		kfree(rq->buf_info[0]);


You can remove those ifs as well.