linux-kernel - Re: [PATCH 5/5] uio: Implement hotunplug support, using libunload

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Message-ID: <20101004123447.GB9961@silverbox.local>
Date:	Mon, 4 Oct 2010 14:34:47 +0200
From:	"Hans J. Koch" <hjk@...utronix.de>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Greg KH <greg@...ah.com>, Greg KH <gregkh@...e.de>,
	"Hans J. Koch" <hjk@...utronix.de>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 5/5] uio: Implement hotunplug support, using libunload

On Sun, Sep 26, 2010 at 03:49:03PM -0700, Eric W. Biederman wrote:
> 
> With this change it is possible to remove a module that implements
> a uio device, or to remove the underlying hardware device of a uio
> device withot crashing the kernel, or causing user space more problems
> than just an I/O error.

Well, that I/O error can also be a segfault if userspace accesses
memory previously mmap'ed. So a userspace program needs to properly
handle -EIO from read(), and has to handle SIG_SEGV. This should also
be mentioned in Documentation/DocBook/uio-howto.tmpl.
Or do you have a better solution?

Thanks,
Hans

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