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
libguestfs lets you edit virtual machines. Supports shell scripting,
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/* Test if F_DUPFD_CLOEXEC works right.
* by Richard W.M. Jones.
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <assert.h>
int
main ()
{
char *file = "/tmp/cloexec.tmp";
int fd = creat (file, 0600);
int fd2;
int flags;
assert (fd >= 0);
fd2 = fcntl (fd, F_DUPFD_CLOEXEC, 0);
assert (fd2 >= 0);
flags = fcntl (fd2, F_GETFD);
assert (flags >= 0);
if ((flags & FD_CLOEXEC) == 0) {
fprintf (stderr, "F_DUPFD_CLOEXEC failed to set FD_CLOEXEC flag!\n");
exit (EXIT_FAILURE);
}
exit (EXIT_SUCCESS);
}
