Re: bash: Fails to upgrade in kFreeBSD jails

[Jonathan Nieder <jrnieder@gmail.com>]

Hi,

Steven Chamberlain wrote:

> Hmmm, I can't seem to reproduce the problem here, in a kfreebsd-i386
> jail environment on a GNU/kFreeBSD (9.0) host.  I had bash 4.2-2 already
> installed though.
>
> I'm trying "apt-get --reinstall install bash" or directly running
> /var/lib/dpkg/info/bash.preinst
>
> Here's a system call trace:
>
>  72202 bash.preinst CALL  open(0x8049678,0x1<><invalid>1,<unused>0)
>  72202 bash.preinst NAMI  "/dev/null"
>  72202 bash.preinst RET   open 3
>  72202 bash.preinst CALL  fcntl(0x3,<invalid=3>,0x8149)
>  72202 bash.preinst RET   fcntl 1
>  72202 bash.preinst CALL  fcntl(0x3,<invalid=4>,0x1<><invalid>1)
>  72202 bash.preinst RET   fcntl 0
>
> Successfully opened /dev/null as fd 0x3.  I assume that is fcntl()
> F_GETFL returning flags = 0x1 (which actually means FD_CLOEXEC was
> already set), then F_SETFL returning 0 = success.

That's the first difference from Stefan's trace, so let's start there.
/dev/null is opened with

	sink = open("/dev/null", O_WRONLY);

O_WRONLY == 1, so this matches the open call in your trace.  So far so
good.  Then we try to set the FD_CLOEXEC flag:

	if (sink >= 0)
		set_cloexec(sink);

set_cloexec() is defined in terms of fcntl calls that get and set the
file descriptor's flags:

	int flags = fcntl(fd, F_GETFL);
	if (flags < 0 || fcntl(fd, F_SETFL, flags | FD_CLOEXEC))
		die_errno("cannot set close-on-exec flag");

F_GETFL is 3, so fcntl is being called correctly.  But why does
fcntl(F_GETFL) return 1 (== FD_CLOEXEC)?  This looks like a bug.  What
kfreebsd-image-(foo) package are you using, and at what version?

Puzzled,
Jonathan