linux-kernel - Re: [RFC][PATCHES] iov

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Date:	Tue, 9 Dec 2014 04:21:35 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: [RFC][PATCHES] iov_iter.c rewrite

On Tue, Dec 09, 2014 at 01:56:51AM +0000, Al Viro wrote:
> On Mon, Dec 08, 2014 at 07:28:17PM +0000, Al Viro wrote:
> > On Mon, Dec 08, 2014 at 10:57:31AM -0800, Linus Torvalds wrote:
> > > So the whole "get_page()" thing is broken. Iterating over pages in a
> > > KVEC is simply wrong, wrong, wrong. It needs to fail.
> > 
> > Well, _that_ is easy to do, of course...  E.g. by replacing that thing in
> > iov_iter_get_pages()/iov_iter_get_pages_alloc() with ({ return -EFAULT; })
> > will do it.
> 
> OK, folded and pushed (i.e. in vfs.git#iov_iter and vfs.git#for-next).
> Matches earlier behaviour; oops reproducer is easy -
> 
> dd if=/dev/zero of=foo.ko bs=4096 count=1
> cat >a.c <<'EOF'
> #define _GNU_SOURCE
> #include <unistd.h>
> #include <fcntl.h>
> #include <sys/stat.h>
> #include <sys/syscall.h>
> main()
> {
>         int fd = open("foo.ko", 00040000);
>         syscall(__NR_finit_module, fd, "", 0);
> }
> EOF
> gcc a.c
> strace ./a.out
> 
> Correct behaviour (both the mainline and this series with fixes folded):
> open("foo.ko", O_RDONLY|O_DIRECT)       = 3
> finit_module(3, "", 0)                  = -1 EFAULT (Bad address)
> Incorrect one:
> open("foo.ko", O_RDONLY|O_DIRECT)       = 3
> finit_module(3, "", 0 <unfinished ...>
> +++ killed by SIGKILL +++
> Killed
> 
> with that oops reproduced.  Not sure if it's a proper LTP or xfstests fodder,
> but anyway, here it is.
> 
> Incremental from previous for-next is

Works for me.

-- 
 Kirill A. Shutemov
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