linux-kernel - Re: [PATCH] vfio/pci: remove a bogus cast in vfio_msi_set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 28 May 2018 21:27:18 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] vfio/pci: remove a bogus cast in vfio_msi_set_block()

Hi Dan,

On 05/28/2018 09:47 AM, Dan Carpenter wrote:
> This cast is confusing...  The "start" variable is an unsigned int.  We
> absolutely do not want to cast it to a negative int so why is the cast
> there?  It turns out, when you look at the context, it's a no-op and we
> can just remove it.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> 
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 1c46045b0e7f..2724fed62129 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -368,7 +368,7 @@ static int vfio_msi_set_block(struct vfio_pci_device *vdev, unsigned start,
>  	}
>  
>  	if (ret) {
> -		for (--j; j >= (int)start; j--)
> +		for (--j; j >= start; j--)
I think this was done one purpose as j can be -1 while start is an
unsigned.

See b95d9305e8cb8d432ca02da1b759fef59bc50ace
"../.., -1 being compared as unsigned doesn't produce the intended stop
condition."

If I remember correctly this led to a bug.

Thanks

Eric
>  			vfio_msi_set_vector_signal(vdev, j, -1, msix);
>  	}
>  
>