linux-kernel - Re: [PATCH 5/7] FUSE: implement ioctl support

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Message-ID: <48B6EF98.4070008@kernel.org>
Date:	Thu, 28 Aug 2008 20:34:00 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Miklos Szeredi <miklos@...redi.hu>
CC:	greg@...ah.com, fuse-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] FUSE: implement ioctl support

Miklos Szeredi wrote:
>> Hmmm... I was trying to stay within similar operation mechanics as other
>> ops.  Directly accessing the caller's memory has performance benefits
>> but that benefit can also be used by reads and writes.  So, if we're
>> gonna do direct memory access, maybe doing it in more generic way is a
>> better idea?
> 
> On the contrary: playing VM games is going to be slow.  I think this
> approach is best suited for generic ioctl support because it
> simplifies the kernel part.  I'd hate to add all that complexity to
> the kernel if not absolutely necessary.

Well, it's only 240 lines with good amount of comments and iovec copying
function.  The ioctl itself isn't too complex.  I'm a bit skeptical
about direct access.  It can easily introduce security vulnerabilities
as there really is no way to hold a pid.

Thanks.

-- 
tejun
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