[regression] F_DUPFD_CLOEXEC breakage fix

[Al Viro <viro@ZenIV.linux.org.uk>]

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.

Interesting...  Oh, crap.  OK, that's easily fixed: in fs/fcntl.c
                err = f_dupfd(arg, filp, FD_CLOEXEC);
should get s/FD_/O_/.  Linus, could you apply the following?

Fix a braino in F_DUPFD_CLOEXEC; f_dupfd() expects flags for
alloc_fd()/get_unused_fd()/etc. and there clone-on-exec if
O_CLOEXEC, not FD_CLOEXEC.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 8f70429..71a600a 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -258,7 +258,7 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 		err = f_dupfd(arg, filp, 0);
 		break;
 	case F_DUPFD_CLOEXEC:
-		err = f_dupfd(arg, filp, FD_CLOEXEC);
+		err = f_dupfd(arg, filp, O_CLOEXEC);
 		break;
 	case F_GETFD:
 		err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;