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Message-ID: <0f94623c-47e2-31e6-50ac-1d11ba061411@embeddedor.com>
Date: Fri, 27 Jul 2018 21:47:17 -0500
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Jinbum Park <jinb.park7@...il.com>, axboe@...nel.dk,
bart.vanassche@....com, jiufei.xue@...ux.alibaba.com
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] pktcdvd: Fix possible Spectre-v1 for pkt_devs
On 07/27/2018 09:30 PM, Jinbum Park wrote:
> User controls @dev_minor which to be used as index of pkt_devs.
> So, It can be exploited via Spectre-like attack. (speculative execution)
>
> This kind of attack leaks address of pkt_devs, [1]
> It leads an attacker to bypass security mechanism such as KASLR.
>
> So sanitize @dev_minor before using it to prevent attack.
>
> [1] https://github.com/jinb-park/linux-exploit/
> tree/master/exploit-remaining-spectre-gadget/leak_pkt_devs.c
>
> Signed-off-by: Jinbum Park <jinb.park7@...il.com>
> ---
> v2: Fix coding style by Gustavo.
>
> drivers/block/pktcdvd.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
> index c61d20c..8ec2eaa 100644
> --- a/drivers/block/pktcdvd.c
> +++ b/drivers/block/pktcdvd.c
> @@ -67,8 +67,8 @@
> #include <scsi/scsi.h>
> #include <linux/debugfs.h>
> #include <linux/device.h>
> -
> #include <linux/uaccess.h>
> +#include <linux/nospec.h>
>
> #define DRIVER_NAME "pktcdvd"
>
> @@ -2231,6 +2231,7 @@ static struct pktcdvd_device *pkt_find_dev_from_minor(unsigned int dev_minor)
> {
> if (dev_minor >= MAX_WRITERS)
> return NULL;
> + dev_minor = array_index_nospec(dev_minor, MAX_WRITERS);
Adding a blank line here would be even better.
> return pkt_devs[dev_minor];
> }
>
>
Acked-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
Thanks
--
Gustavo
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