linux-kernel - Re: [PATCH] fbcon -- fix race between open and removal of framebuffers

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:	Thu, 05 May 2011 22:00:42 +0100
From:	Jack Stone <jwjstone@...tmail.fm>
To:	tim.gardner@...onical.com
CC:	linux-fbdev@...r.kernel.org, lethal@...ux-sh.org,
	linux-kernel@...r.kernel.org, Andy Whitcroft <apw@...onical.com>,
	Leann Ogasawara <leann.ogasawara@...onical.com>
Subject: Re: [PATCH] fbcon -- fix race between open and removal of framebuffers

On 05/05/2011 18:41, tim.gardner@...onical.com wrote:
> +static struct fb_info *get_framebuffer_info(int idx)
> +__acquires(&registered_lock)
> +__releases(&registered_lock)
> +{
> +	struct fb_info *fb_info;
> +
> +	spin_lock(&registered_lock);
> +	fb_info = registered_fb[idx];
> +	fb_info->ref_count++;
> +	spin_unlock(&registered_lock);
> +
> +	return fb_info;
> +}
> +
>  static int
>  fb_open(struct inode *inode, struct file *file)
>  __acquires(&info->lock)
> @@ -1363,13 +1421,17 @@ __releases(&info->lock)
>  
>  	if (fbidx >= FB_MAX)
>  		return -ENODEV;
> -	info = registered_fb[fbidx];
> +	info = get_framebuffer_info(fbidx);
>  	if (!info)
>  		request_module("fb%d", fbidx);
> -	info = registered_fb[fbidx];
> +	info = get_framebuffer_info(fbidx);
>  	if (!info)
>  		return -ENODEV;

If the first get_framebuffer_info succeeds don't you up the ref count
twice? Shouldn't this be:

info = get_framebuffer_info(fbidx);
if (!info) {
	request_module("fb%d", fbidx);
	info = get_framebuffer_info(fbidx);
}
if (!info)
	return -ENODEV;

Thanks,

Jack
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/