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From: Christoph Hellwig <hch@lst.de>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Ian Kent <raven@themaw.net>, David Howells <dhowells@redhat.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	netfilter-devel@vger.kernel.org
Subject: Re: [PATCH 09/14] fs: don't change the address limit for ->write_iter in __kernel_write
Date: Fri, 29 May 2020 07:57:36 +0200
Message-ID: <20200529055736.GB6788@lst.de> (raw)
In-Reply-To: <20200528190052.GM23230@ZenIV.linux.org.uk>

On Thu, May 28, 2020 at 08:00:52PM +0100, Al Viro wrote:
> On Thu, May 28, 2020 at 07:40:38AM +0200, Christoph Hellwig wrote:
> > If we write to a file that implements ->write_iter there is no need
> > to change the address limit if we send a kvec down.  Implement that
> > case, and prefer it over using plain ->write with a changed address
> > limit if available.
> 
> Umm...  It needs a comment along the lines of "weird shits like
> /dev/sg that currently check for uaccess_kernel() will just
> have to make sure they never switch to ->write_iter()"

sg and hid has the uaccess_kernel because it accesses userspace memory not
in the range passed to it.  Something using write_iter/read_iter should
never access any memory outside the iter passed to.  rdma has it because
it uses write as a bidirectional interface, which obviously can't work at
all with an iter.  So I'm not sure what we should comment on, but if
you have a desire and a proposal for a comment I'll happily add it.

  reply index

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-28  5:40 clean up kernel_{read,write} & friends v2 Christoph Hellwig
2020-05-28  5:40 ` [PATCH 01/14] cachefiles: switch to kernel_write Christoph Hellwig
2020-05-28  5:40 ` [PATCH 02/14] autofs: " Christoph Hellwig
2020-05-28  5:40 ` [PATCH 03/14] bpfilter: " Christoph Hellwig
2020-05-28  5:40 ` [PATCH 04/14] fs: unexport __kernel_write Christoph Hellwig
2020-05-28  5:40 ` [PATCH 05/14] fs: check FMODE_WRITE in __kernel_write Christoph Hellwig
2020-05-28  5:40 ` [PATCH 06/14] fs: remove the call_{read,write}_iter functions Christoph Hellwig
2020-05-28 18:56   ` Al Viro
2020-05-29  5:51     ` Christoph Hellwig
2020-05-28  5:40 ` [PATCH 07/14] fs: implement kernel_write using __kernel_write Christoph Hellwig
2020-05-28  5:40 ` [PATCH 08/14] fs: remove __vfs_write Christoph Hellwig
2020-05-28  5:40 ` [PATCH 09/14] fs: don't change the address limit for ->write_iter in __kernel_write Christoph Hellwig
2020-05-28 18:43   ` Linus Torvalds
2020-05-29 12:32     ` Christoph Hellwig
2020-05-31 23:59       ` Logan Gunthorpe
2020-05-28 19:00   ` Al Viro
2020-05-29  5:57     ` Christoph Hellwig [this message]
2020-05-29 13:37       ` Christoph Hellwig
2020-05-28  5:40 ` [PATCH 10/14] fs: add a __kernel_read helper Christoph Hellwig
2020-05-28  5:40 ` [PATCH 11/14] integrity/ima: switch to using __kernel_read Christoph Hellwig
2020-05-28  5:40 ` [PATCH 12/14] fs: implement kernel_read " Christoph Hellwig
2020-05-28  5:40 ` [PATCH 13/14] fs: remove __vfs_read Christoph Hellwig
2020-05-28  5:40 ` [PATCH 14/14] fs: don't change the address limit for ->read_iter in __kernel_read Christoph Hellwig
2020-05-28 19:03   ` Al Viro
2020-05-28 18:51 ` clean up kernel_{read,write} & friends v2 Linus Torvalds
2020-05-28 18:57   ` Sedat Dilek
2020-05-28 19:22   ` Joe Perches
2020-05-28 19:33     ` Al Viro
2020-05-28 19:44       ` Matthew Wilcox
2020-05-28 20:06         ` Al Viro
2020-05-28 20:14           ` Deucher, Alexander
2020-05-28 20:18         ` Joe Perches
2020-05-28 20:29       ` Dave Airlie
2020-05-28 21:03     ` Joe Perches
2020-05-28 20:17 ` David Howells
2020-05-28 21:20   ` Casey Schaufler
2020-05-29 13:08     ` David Laight
2020-05-29 19:19       ` Linus Torvalds
2020-05-29 22:02         ` Casey Schaufler
2020-05-29 23:12         ` [PATCH] checkpatch/coding-style: Allow 100 column lines Joe Perches
2020-05-30 22:14           ` Andreas Dilger
2020-05-30 23:15             ` Joe Perches
2020-06-05  6:36         ` clean up kernel_{read,write} & friends v2 Philippe Mathieu-Daudé
2020-06-05 15:00           ` Nicolas Pitre
  -- strict thread matches above, loose matches on Subject: below --
2020-05-13  6:56 Christoph Hellwig
2020-05-13  6:56 ` [PATCH 09/14] fs: don't change the address limit for ->write_iter in __kernel_write Christoph Hellwig
     [not found] ` <20200516030436.19448-1-hdanton@sina.com>
2020-05-18  6:42   ` Christoph Hellwig

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