netdev - Re: [PATCH AUTOSEL 5.15 13/16] vdpa: clean up get_config

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Date:   Sat, 2 Apr 2022 06:57:49 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Laura Abbott <labbott@...nel.org>,
        Luo Likang <luolikang@...ocus.com>,
        "Michael S . Tsirkin" <mst@...hat.com>, jasowang@...hat.com,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, oss-security@...ts.openwall.com
Subject: Re: [PATCH AUTOSEL 5.15 13/16] vdpa: clean up get_config_size ret
 value handling

The mitre.org page

https://cve.mitre.org/cgi-bin/cvename.cgi?name=2022-0998

says this is a fix for CVE-2022-0998 but if you apply it by itself it
creates a serious security problem.  Originally this bug only affected
32 bit systems but this patch will change it to affect everyone.

You need to apply commit 3ed21c1451a1 ("vdpa: check that offsets are
within bounds").

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3ed21c1451a14d139e1ceb18f2fa70865ce3195a

I don't know if this affects anyone, but it seemed worth mentioning.

regards,
dan carpenter

On Sat, Jan 22, 2022 at 07:12:12PM -0500, Sasha Levin wrote:
> From: Laura Abbott <labbott@...nel.org>
> 
> [ Upstream commit 870aaff92e959e29d40f9cfdb5ed06ba2fc2dae0 ]
> 
> The return type of get_config_size is size_t so it makes
> sense to change the type of the variable holding its result.
> 
> That said, this already got taken care of (differently, and arguably
> not as well) by commit 3ed21c1451a1 ("vdpa: check that offsets are
> within bounds").
> 
> The added 'c->off > size' test in that commit will be done as an
> unsigned comparison on 32-bit (safe due to not being signed).
> 
> On a 64-bit platform, it will be done as a signed comparison, but in
> that case the comparison will be done in 64-bit, and 'c->off' being an
> u32 it will be valid thanks to the extended range (ie both values will
> be positive in 64 bits).
> 
> So this was a real bug, but it was already addressed and marked for stable.
> 
> Signed-off-by: Laura Abbott <labbott@...nel.org>
> Reported-by: Luo Likang <luolikang@...ocus.com>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  drivers/vhost/vdpa.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index d62f05d056b7b..913cd465f9f1e 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -195,7 +195,7 @@ static int vhost_vdpa_config_validate(struct vhost_vdpa *v,
>  				      struct vhost_vdpa_config *c)
>  {
>  	struct vdpa_device *vdpa = v->vdpa;
> -	long size = vdpa->config->get_config_size(vdpa);
> +	size_t size = vdpa->config->get_config_size(vdpa);
>  
>  	if (c->len == 0 || c->off > size)
>  		return -EINVAL;
> -- 
> 2.34.1
> 
>