Re: [regression] F_DUPFD_CLOEXEC breakage fix

[Richard W.M. Jones]

On Mon, Oct 08, 2012 at 11:21:58PM +0100, Al Viro wrote:
> 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 <address@hidden>

I can confirm that this patch fixed the problem for me.

Tested-by: Richard W.M. Jones <address@hidden>

> ---
> 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;

Rich.

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