linux-kernel - Re: [PATCH] staging: comedi: Fix comedi_device refcnt leak in comedi

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] [day] [month] [year] [list]

Message-ID: <a5988c23-e552-b787-feb0-2d1bda8f1668@mev.co.uk>
Date:   Mon, 20 Apr 2020 11:15:12 +0100
From:   Ian Abbott <abbotti@....co.uk>
To:     Xiyu Yang <xiyuyang19@...an.edu.cn>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Xin Tan <tanxin.ctf@...il.com>, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, kjlu@....edu
Subject: Re: [PATCH] staging: comedi: Fix comedi_device refcnt leak in
 comedi_open

On 20/04/2020 06:44, Xiyu Yang wrote:
> comedi_open() invokes comedi_dev_get_from_minor(), which returns a
> reference of the COMEDI device to "dev" with increased refcount.
> 
> When comedi_open() returns, "dev" becomes invalid, so the refcount
> should be decreased to keep refcount balanced.
> 
> The reference counting issue happens in one exception handling path of
> comedi_open(). When "cfp" allocation is failed, the refcnt increased by
> comedi_dev_get_from_minor() is not decreased, causing a refcnt leak.
> 
> Fix this issue by calling comedi_dev_put() on this error path when "cfp"
> allocation is failed.
> 
> Fixes: 20f083c07565 ("staging: comedi: prepare support for per-file read
> and write subdevices")
> Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
> ---
>   drivers/staging/comedi/comedi_fops.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
> index 08d1bbbebf2d..e84b4fb493d6 100644
> --- a/drivers/staging/comedi/comedi_fops.c
> +++ b/drivers/staging/comedi/comedi_fops.c
> @@ -2725,8 +2725,10 @@ static int comedi_open(struct inode *inode, struct file *file)
>   	}
>   
>   	cfp = kzalloc(sizeof(*cfp), GFP_KERNEL);
> -	if (!cfp)
> +	if (!cfp) {
> +		comedi_dev_put(dev);
>   		return -ENOMEM;
> +	}
>   
>   	cfp->dev = dev;
>   
> 

Thanks for spotting that!

Signed-off-by: Ian Abbott <abbotti@....co.uk>

-- 
-=( Ian Abbott <abbotti@....co.uk> || Web: www.mev.co.uk )=-
-=( MEV Ltd. is a company registered in England & Wales. )=-
-=( Registered number: 02862268.  Registered address:    )=-
-=( 15 West Park Road, Bramhall, STOCKPORT, SK7 3JZ, UK. )=-