Date: Tue, 17 May 2005 06:00:25 +0100
From: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
To: Greg K-H <greg@kroah.com>
Cc: linux-kernel@vger.kernel.org, petero2@telia.com
Subject: Re: [PATCH] Fix root hole in pktcdvd
Message-ID: <20050517050025.GP1150@parcelfarce.linux.theplanet.co.uk>
References: <11163046681444@kroah.com> <11163046692974@kroah.com>
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On Mon, May 16, 2005 at 09:37:49PM -0700, Greg KH wrote:
> ioctl_by_bdev may only be used INSIDE the kernel.  If the "arg" argument
> refers to memory that is accessed by put_user/get_user in the ioctl
> function, the memory needs to be in the kernel address space (that's the
> set_fs(KERNEL_DS) doing in the ioctl_by_bdev).  This works on i386 because
> even with set_fs(KERNEL_DS) the user space memory is still accessible with
> put_user/get_user.  That is not true for s390.  In short the ioctl
> implementation of the pktcdvd device driver is horribly broken.

Same comment as for previous patch.  I'll take a look at that sucker,
it might happen to be OK, seeing that most of the bdev ->ioctl() instances
ignore file argument and we might get away with passing odd stuff to
anything that could occur here.
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