linux-kernel - F_DUPFD_CLOEXEC broken in 3.7.0

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Date:	Mon, 8 Oct 2012 23:05:32 +0100
From:	"Richard W.M. Jones" <rjones@...hat.com>
To:	Jim Meyering <jim@...ering.net>, eblake@...hat.com
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>
Subject: F_DUPFD_CLOEXEC broken in 3.7.0

Let's move this to LKML ...

On Mon, Oct 08, 2012 at 10:53:25PM +0100, Richard W.M. Jones wrote:
> On Mon, Oct 08, 2012 at 10:50:30PM +0100, Richard W.M. Jones wrote:
> [.. discussion on gnulib test-cloexec test snipped ..]
> > I'm suspicious this is a kernel bug:
> > 
> > creat("test-cloexec.tmp", 0600)         = 3
> > fcntl(3, F_GETFD)                       = 0
> > fcntl(3, F_GETFD)                       = 0
> > fcntl(3, F_SETFD, FD_CLOEXEC)           = 0
> > fcntl(3, F_GETFD)                       = 0x1 (flags FD_CLOEXEC)
> > fcntl(3, F_GETFD)                       = 0x1 (flags FD_CLOEXEC)
> > fcntl(3, F_SETFD, 0)                    = 0
> > fcntl(3, F_GETFD)                       = 0
> > fcntl(3, F_DUPFD_CLOEXEC, 0)            = 4
> > fcntl(4, F_GETFD)                       = 0
> > write(2, "test-cloexec.c:97: assertion failed\n", 36) = 36
> > 
> > It seems to me from the description in the man page that
> > F_DUPFD_CLOEXEC ought to be setting the FD_CLOEXEC flag on file
> > descriptor 4, so either it's not or else F_GETFD isn't reading the
> > flag for some reason.
> 
> Al Viro (CC'd) made some changes in this area recently ..

Attached is a self-contained test program that demonstrates the bug.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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View attachment "cloexec.c" of type "text/plain" (579 bytes)