linux-kernel - Re: [PATCH] hv_netvsc: Add check for kvmalloc

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Message-ID: <Yi7xCSdtTmSgIcgp@kroah.com>
Date:   Mon, 14 Mar 2022 08:38:49 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>
Cc:     stephen@...workplumber.org, kys@...rosoft.com,
        haiyangz@...rosoft.com, sthemmin@...rosoft.com, wei.liu@...nel.org,
        decui@...rosoft.com, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, hawk@...nel.org,
        john.fastabend@...il.com, andrii@...nel.org, kafai@...com,
        songliubraving@...com, yhs@...com, kpsingh@...nel.org,
        linux-hyperv@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH] hv_netvsc: Add check for kvmalloc_array

On Mon, Mar 14, 2022 at 03:33:49PM +0800, Jiasheng Jiang wrote:
> On Fri, Mar 11, 2022 at 02:43:48PM +0800, Greg KH wrote:
> >> As the potential failure of the kvmalloc_array(),
> >> it should be better to check and restore the 'data'
> >> if fails in order to avoid the dereference of the
> >> NULL pointer.
> >> 
> >> Fixes: 6ae746711263 ("hv_netvsc: Add per-cpu ethtool stats for netvsc")
> >> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
> >> ---
> >>  drivers/net/hyperv/netvsc_drv.c | 6 ++++++
> >>  1 file changed, 6 insertions(+)
> >> 
> >> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> >> index 3646469433b1..018c4a5f6f44 100644
> >> --- a/drivers/net/hyperv/netvsc_drv.c
> >> +++ b/drivers/net/hyperv/netvsc_drv.c
> >> @@ -1587,6 +1587,12 @@ static void netvsc_get_ethtool_stats(struct net_device *dev,
> >>  	pcpu_sum = kvmalloc_array(num_possible_cpus(),
> >>  				  sizeof(struct netvsc_ethtool_pcpu_stats),
> >>  				  GFP_KERNEL);
> >> +	if (!pcpu_sum) {
> >> +		for (j = 0; j < i; j++)
> >> +			data[j] = 0;
> >> +		return;
> >> +	}
> > 
> >How did you test this to verify it is correct?
> 
> Thanks, I have tested the patch by kernel_patch_verify,

What is that?

> and all the tests are passed.

What tests exactly?  How did you fail this allocation?

thanks,

greg k-h