From: Al Viro <viro@ZenIV.linux.org.uk>
To: Dave Chinner <david@fromorbit.com>
Cc: Dave Jones <davej@codemonkey.org.uk>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
linux-xfs@vger.kernel.org
Subject: Re: iov_iter_pipe warning.
Date: Tue, 12 Sep 2017 12:13:08 +0100 [thread overview]
Message-ID: <20170912111308.GM5426@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20170912060214.GS17782@dastard>
On Tue, Sep 12, 2017 at 04:02:14PM +1000, Dave Chinner wrote:
> > Note that one of the bugs there applies to normal read() as well - if you
> > are reading from a hole in file into an array with a read-only page in
> > the middle, you want a short read.
>
> And there's another WTF? moment.....
>
> How do we get a read only page in the middle of an array of pages
> we've been told to write data into? And why isn't that a bug in the
> code that supplied us with those pages?
Sorry, I'd been unclear - I'm talking about read(2) or readv(2) called by
userland with a read-only piece in the middle of a (user-supplied) buffer.
Either due to mprotect() or simply with one of the iovecs passed to readv(2)
having ->iov_base set to some read-only area.
It may be a bug in userland code, but when handling that error is as trivial
as "don't assume iov_iter_zero(to, n) will return n, use the actual return
value", resorting to "the userland code was probably buggy and it's O_DIRECT,
so we can do whatever we want" looks wrong.
next prev parent reply other threads:[~2017-09-12 11:13 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20170412152600.GP29622@ZenIV.linux.org.uk>
[not found] ` <20170412162709.bn5qfk4seues3yos@codemonkey.org.uk>
[not found] ` <20170412170723.GQ29622@ZenIV.linux.org.uk>
[not found] ` <20170412190318.srkkdytf2ebrjzrg@codemonkey.org.uk>
[not found] ` <20170421175430.GT29622@ZenIV.linux.org.uk>
[not found] ` <20170428152955.mafs3f22srmm34aw@codemonkey.org.uk>
[not found] ` <20170428164313.GK29622@ZenIV.linux.org.uk>
[not found] ` <20170428165024.ofyl2atpjwohekqa@codemonkey.org.uk>
[not found] ` <20170428172024.GL29622@ZenIV.linux.org.uk>
[not found] ` <20170807201818.kykqzexce6ap6aik@codemonkey.org.uk>
2017-08-28 20:31 ` iov_iter_pipe warning Dave Jones
2017-08-29 4:25 ` Darrick J. Wong
2017-08-30 17:05 ` Dave Jones
2017-08-30 17:13 ` Darrick J. Wong
2017-08-30 17:17 ` Dave Jones
2017-09-06 20:03 ` Dave Jones
2017-09-06 23:46 ` Dave Chinner
2017-09-07 3:48 ` Dave Jones
2017-09-07 4:33 ` Al Viro
2017-09-08 1:04 ` Al Viro
2017-09-10 1:07 ` Dave Jones
2017-09-10 2:57 ` Al Viro
2017-09-10 16:07 ` Dave Jones
2017-09-10 20:05 ` Al Viro
2017-09-10 20:07 ` Dave Jones
2017-09-10 20:33 ` Al Viro
2017-09-10 21:11 ` Dave Chinner
2017-09-10 21:19 ` Al Viro
2017-09-10 22:08 ` Dave Chinner
2017-09-10 23:07 ` Al Viro
2017-09-10 23:15 ` Al Viro
2017-09-11 0:31 ` Dave Chinner
2017-09-11 3:32 ` Al Viro
2017-09-11 6:44 ` Dave Chinner
2017-09-11 20:07 ` Al Viro
2017-09-11 20:17 ` Al Viro
2017-09-12 6:02 ` Dave Chinner
2017-09-12 11:13 ` Al Viro [this message]
2017-09-11 12:07 ` Christoph Hellwig
2017-09-11 12:51 ` Al Viro
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