linux-kernel - Re: [patch 9/9] compat_ioctl: fix compat_fd

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Message-ID: <20071007095955.GR8181@ftp.linux.org.uk>
Date:	Sun, 7 Oct 2007 10:59:55 +0100
From:	Al Viro <viro@....linux.org.uk>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Jens Axboe <jens.axboe@...cle.com>, linux-kernel@...r.kernel.org,
	davem@...emloft.net, hch@....de
Subject: Re: [patch 9/9] compat_ioctl: fix compat_fd_ioctl pointer access

On Sat, Oct 06, 2007 at 08:19:11PM +0200, Arnd Bergmann wrote:
> As found by sparse, a user space pointer is assigned to a kernel
> data structure while calling other code with set_fs(KERNEL_DS),
> which could lead to leaking kernel data if that pointer is
> ever accessed.
> 
> I could not find any place in the floppy drivers that actually
> uses that pointer, but assigning it to an empty string is
> a safer choice and gets rid of the sparse warning.

FWIW, I'd kill kmalloc(), switched to compat_alloc_user_space() and
copy_in_user() / get_user()+put_user().  And kill set_fs() around that
sys_ioctl()...  Separate from the rest of this series, though.
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