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Subject: Re: [PATCH 186/190] Revert "virt: vbox: Only copy_from_user the
 request-header once"
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
Cc:     Wenwen Wang <wang6495@umn.edu>
References: <20210421130105.1226686-1-gregkh@linuxfoundation.org>
 <20210421130105.1226686-187-gregkh@linuxfoundation.org>
From:   Hans de Goede <hdegoede@redhat.com>
Message-ID: <68067532-56e5-c135-7a7e-0743c8e7b2a0@redhat.com>
Date:   Wed, 21 Apr 2021 18:51:24 +0200
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Hi Greg,

On 4/21/21 3:01 PM, Greg Kroah-Hartman wrote:
> This reverts commit bd23a7269834dc7c1f93e83535d16ebc44b75eba.
> 
> Commits from @umn.edu addresses have been found to be submitted in "bad
> faith" to try to test the kernel community's ability to review "known
> malicious" changes.  The result of these submissions can be found in a
> paper published at the 42nd IEEE Symposium on Security and Privacy
> entitled, "Open Source Insecurity: Stealthily Introducing
> Vulnerabilities via Hypocrite Commits" written by Qiushi Wu (University
> of Minnesota) and Kangjie Lu (University of Minnesota).
> 
> Because of this, all submissions from this group must be reverted from
> the kernel tree and will need to be re-reviewed again to determine if
> they actually are a valid fix.  Until that work is complete, remove this
> change to ensure that no problems are being introduced into the
> codebase.
> 
> Cc: Wenwen Wang <wang6495@umn.edu>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Ugh what a mess (the whole umn.edu thing).

I still remember reviewing this patch during its original submission
and I've reviewed it again this morning when you just send it out.

And now after letting it sit for a bit I've reviewed it a third time
and it seems to do what it says on the label / in the original commit
msg; and if fixes a real, potentially security, issue.

I'm not sure what the process is for "good" patches in the set
which you are reverting. I would prefer for this patch to be dropped
from the set of reveert. But I can also submit a revert of the revert(?)
once this set of reverts has been merged.

Regards,

Hans


> ---
>  drivers/virt/vboxguest/vboxguest_linux.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/virt/vboxguest/vboxguest_linux.c b/drivers/virt/vboxguest/vboxguest_linux.c
> index 73eb34849eab..f5cd9cfa1ef6 100644
> --- a/drivers/virt/vboxguest/vboxguest_linux.c
> +++ b/drivers/virt/vboxguest/vboxguest_linux.c
> @@ -142,9 +142,7 @@ static long vbg_misc_device_ioctl(struct file *filp, unsigned int req,
>  	if (!buf)
>  		return -ENOMEM;
>  
> -	*((struct vbg_ioctl_hdr *)buf) = hdr;
> -	if (copy_from_user(buf + sizeof(hdr), (void *)arg + sizeof(hdr),
> -			   hdr.size_in - sizeof(hdr))) {
> +	if (copy_from_user(buf, (void *)arg, hdr.size_in)) {
>  		ret = -EFAULT;
>  		goto out;
>  	}
>