On Mon, 15 Nov 2010, Karl-Johan Karlsson wrote:
> Hi,
>
> (Please Cc: me since I'm not subscribed to linux-fsdevel)
>
> My initrd, which worked in 2.6.35, is broken in 2.6.36. I bisected it to this
> commit:
>
> commit 8df9d1a4142311c084ffeeacb67cd34d190eff74
> Author: Miklos Szeredi <mszeredi@xxxxxxx>
> Date: Tue Aug 10 11:41:41 2010 +0200
>
> vfs: show unreachable paths in getcwd and proc
>
> Prepend "(unreachable)" to path strings if the path is not reachable
> from the current root.
>
> My root partition is encrypted with dm-crypt, and the key is encrypted with a
> passphrase using GnuPG and stored in the initrd. To set this up, the initrd
> does:
>
> gpg --quiet -d /boot/root-key.gpg | cryptsetup -h plain -c aes-xts-plain \
> -s 512 create cryptroot /dev/sda3
>
> To read the passphrase, gpg spawns pinentry-curses and configures it using
> text commands on stdin. Since the above commit, this breaks when setting the
> TTY from which to read the passphrase:
>
> [pid 1129] readlink("/proc/self/fd/0", "(unreachable)/dev/console"..., 4095)
> = 25
> [pid 1129] write(7, "OPTION ttyname=(unreachable)/dev/console", 40
> <unfinished ...>
> [pid 1132] <... read resumed> "OPTION ttyname=(unreachable)/dev/console",
> 1002) = 40
> [pid 1132] open("(unreachable)/dev/console", O_RDONLY) = -1 ENOENT (No such
> file or directory)
Blindly trusting readlink on a /proc/*/fd/ file to yield a valid
absolute path has always been wrong.
That readlink comes from a ttyname(3) call, I suppose. A fix to
ttyname() has already been added to glibc git:
0e516e0e Verify in ttyname() that the symlink is valid.
>
> I suppose the real bug is that /dev/console is considered unreachable, when
> (according to strace) no process has done chroot() and the initrd has a
> functioning /dev/console:
>
> crw-r--r-- 1 root root 5, 1 1 jul 2007 dev/console
What filesystem is this on? The original console fd comes from
rootfs, and initrd probably already did a pivot_root().
Thanks,
Miklos
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