Re: [PATCH RESEND] splice: introduce FMODE_SPLICE_READ and FMODE_SPLICE_WRITE

From	Johannes Thumshirn <jthumshirn@suse.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH RESEND] splice: introduce FMODE_SPLICE_READ and FMODE_SPLICE_WRITE
Date	2017-01-11 14:10 +0100
Message-ID	<sYqP7-7ld-11@gated-at.bofh.it> (permalink)
References	<sYnRf-5iP-23@gated-at.bofh.it> <sYqcq-6Ty-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, Jan 11, 2017 at 07:20:13AM -0500, Jeff Layton wrote:
> On Wed, 2017-01-11 at 10:51 +0100, Johannes Thumshirn wrote:
> > Introduce FMODE_SPLICE_READ and FMODE_SPLICE_WRITE. These modes check
> > whether it is legal to read or write a file using splice. Both get
> > automatically set on regular files and are not checked when a 'struct
> > fileoperations' includes the splice_{read,write} methods.
> > 
> 
> Could you add a description of the problem that this solves? I assume
> you hit a problem trying to splice to/from a non-regular file, but it'd
> be good to know what that problem was.

The problem is that a driver's ->write() is called under KERNEL_DS this way.
This happened for sg and bsg and caused 128394eff 'sg_write()/bsg_write() is
not fit to be called under KERNEL_DS' as well as a0ac402cf 'Don't feed
anything but regular iovec's to blk_rq_map_user_iov'.

There have also been patches for InfiniBand AFAIR doing similar things.

So this is to solve it for future abuses.

HTH,
	Johannes
-- 
Johannes Thumshirn                                          Storage
jthumshirn@suse.de                                +49 911 74053 689
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Thread

[PATCH RESEND] splice: introduce FMODE_SPLICE_READ and FMODE_SPLICE_WRITE Johannes Thumshirn <jthumshirn@suse.de> - 2017-01-11 11:00 +0100
  Re: [PATCH RESEND] splice: introduce FMODE_SPLICE_READ and  FMODE_SPLICE_WRITE Jeff Layton <jlayton@redhat.com> - 2017-01-11 13:30 +0100
    Re: [PATCH RESEND] splice: introduce FMODE_SPLICE_READ and  FMODE_SPLICE_WRITE Johannes Thumshirn <jthumshirn@suse.de> - 2017-01-11 14:10 +0100
    Re: [PATCH RESEND] splice: introduce FMODE_SPLICE_READ and  FMODE_SPLICE_WRITE Al Viro <viro@ZenIV.linux.org.uk> - 2017-01-12 10:20 +0100

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