[Libguestfs] libguestfs-test-tool on ubuntu: kernel panic
David Konerding
dek at konerding.com
Wed Aug 10 18:59:47 UTC 2011
OK. I hacked some extra eprintfs into febootstrap.ml (learning a bit of
ocaml in the process). I can confirm that the unpacked debian file has
restrictive permissions:
tmp/febootstrape193191fefe36c245623bc48e5b150a2.tmp/bash_4.1-2ubuntu3_amd64.deb.d$
ls -l bin
total 920
-rwxr-x--- 1 dek redacted 934336 Apr 18 2010 bash
lrwxrwxrwx 1 dek redacted 4 Aug 10 11:43 rbash -> bash
lrwxrwxrwx 1 dek redacted 4 Aug 10 11:43 sh -> bash
which is what is causing the permission check in febootstrap.ml to fail:
else if mode land 0o004 = 0 then
warn_unreadable := path :: !warn_unreadable
It looks like when I extract a package using dpkg-deb directly, it has
permissive permissions,
$ dpkg-deb --extract
/tmp/febootstrap02946e2e929e78a0efa20670d79db1ab.tmp/bash_4.1-2ubuntu3_amd64.deb
/tmp/shoop
$ ls -l /tmp/shoop
total 920
-rwxr-xr-x 1 dek redacted 934336 Apr 18 2010 bash
lrwxrwxrwx 1 dek redacted 4 Aug 10 09:39 rbash -> bash
lrwxrwxrwx 1 dek redacted 4 Aug 10 09:39 sh -> bash
but, febootstrap runs this command:
dpkg-deb --fsys-tarfile
/tmp/febootstrape193191fefe36c245623bc48e5b150a2.tmp/bash_4.1-2ubuntu3_amd64.deb
| (cd
/tmp/febootstrape193191fefe36c245623bc48e5b150a2.tmp/bash_4.1-2ubuntu3_amd64.deb.d
&& tar xf -
which creates a tar file that has this:
-rwxr-xr-x root/root 934336 2010-04-18 19:16 ./bin/bash
which unpacks to:
-rwxr-x--- 1 dek redacted 934336 Apr 18 2010 bash
I think this was happening due to my umask being set to '0027'. I set it to
0000, and I don't get the warning any more, and the generated appliance has
a /bin/bash.
Sorry about the noise. Maybe febootstrap should set a reasonable umask
internally?
On Wed, Aug 10, 2011 at 11:27 AM, David Konerding <dek at konerding.com> wrote:
>
>
> On Wed, Aug 10, 2011 at 10:46 AM, Richard W.M. Jones <rjones at redhat.com>wrote:
>
>> On Wed, Aug 10, 2011 at 09:42:10AM -0700, David Konerding wrote:
>> > BTW, it's actually a list of ~8000 files (looks like all the unpacked
>> files
>> > from all the .debs that got downloadeD).
>> >
>> > I stopped feboostrap during its download after it downloaded the .deb
>> for
>> > bash (there seems to be no option to force febootstrap to not clean up
>> > /tmp/febootstrap* after running).
>> >
>> > I see no reason why feboostrap wouldn't be able to read these files:
>> > 2318338 4 drwxr-xr-x 2 dek redacted 4096 Aug 10 09:39
>> > /tmp/bashpkg/bin
>> > 2318444 0 lrwxrwxrwx 1 dek redacted 4 Aug 10 09:39
>> > /tmp/bashpkg/bin/sh -> bash
>> > 2318443 0 lrwxrwxrwx 1 dek redacted 4 Aug 10 09:39
>> > /tmp/bashpkg/bin/rbash -> bash
>> > 2318339 920 -rwxr-xr-x 1 dek redacted 934336 Apr 18 2010
>> > /tmp/bashpkg/bin/bash
>>
>> I would agree this certainly looks like a bug in febootstrap. I can't
>> imagine what it would be that wouldn't also affect our builds on
>> Ubuntu 11.04.
>>
>> Here is a way you could try reproducing the issue, in a smaller and
>> more manageable context.
>>
>> You can run all of the commands below as non-root from /tmp or another
>> temporary directory.
>>
>> First:
>>
>> $ febootstrap --verbose --names bash
>>
>> then examine the debug messages and the output files created in the
>> current directory ('base.img' and 'hostfiles').
>>
>>
> This fetches bash, dash, and a number of other packages. It reports:
> 1719 files and directories
> febootstrap: warning: some host files are unreadable by non-root
> febootstrap: warning: get your distro to fix these files:
> /bin/bash
> /bin/cat
> /bin/chgrp
> /bin/chmod
> ...
>
> There are 1361 files in the list.
>
>
>> If base.img and hostfiles look reasonable, try building an appliance
>> from them:
>>
>>
> Looking at hostfiles, there is no /bin/bash, but there is /bin/sh and
> /bin/rbash (BTW, Ubuntu uses dash as the main /bin/sh, not bash, but I
> assume that's not relevant). sh is a symlink to bash, as is rbash.
>
> I extracted base.img, and it doesn't include any files in /bin. It looks
> like all the files in that archive are text/config files or symlinks.
>
> $ febootstrap-supermin-helper -f ext2 -v \
>> base.img hostfiles $(uname -m) kernel initrd appliance
>>
>> (Note that 'kernel', 'initrd' and 'appliance' are all output files
>> that will be created in the current directory).
>>
>> Now you've got a chicken-and-egg problem, but 'appliance' is an ext2
>> disk image which can be examined using guestfish:
>>
>> $ guestfish --ro -a appliance -m /dev/sda
>>
>>
> Right. I just mounted it as a loopback image instead... /bin contains only
> this:
> $ ls -l /mnt/appliance/bin
> total 8
> lrwxrwxrwx 1 root root 4 Sep 22 2010 rbash -> bash
> lrwxrwxrwx 1 root root 9 Sep 22 2010 sh -> /bin/bash
>
> Running strace on febootstrap, I see that it stats the /bin/bash in the
> unpacked bash deb pkg at least once successfully:
> 7928
> lstat("/tmp/febootstrape193191fefe36c245623bc48e5b150a2.tmp/bash_4.1-2ubuntu3_amd64.deb.d//bin/bash",
> {st_mode=S_IFREG|0750, st_size=934336, ...}) = 0
> 7928 write(2, "febootstrap: warning: some host files are unreadable by
> non-root\nfebootstrap: warning: get your distro to fix these
> files:\n\t/bin/bash\n", 134) = 134
>
>
>
>> Welcome to guestfish, the libguestfs filesystem interactive shell for
>> editing virtual machine filesystems.
>>
>> Type: 'help' for help on commands
>> 'man' to read the manual
>> 'quit' to quit the shell
>>
>> ><fs> ll /bin/
>> total 2668
>> drwxr-xr-x 2 1000 1000 4096 Aug 10 17:40 .
>> drwxr-xr-x 17 1000 1000 4096 Aug 10 17:41 ..
>> -rwxr-xr-x 1 0 0 954896 Mar 31 21:20 bash
>> -rwxr-xr-x 1 0 0 47696 Feb 23 14:24 cat
>> -rwxr-xr-x 1 0 0 55864 Feb 23 14:24 chgrp
>> -rwxr-xr-x 1 0 0 51704 Feb 23 14:24 chmod
>> -rwxr-xr-x 1 0 0 55880 Feb 23 14:24 chown
>> -rwxr-xr-x 1 0 0 117808 Feb 23 14:24 cp
>> -rwxr-xr-x 1 0 0 109736 Nov 15 2010 dash
>> -rwxr-xr-x 1 0 0 55832 Feb 23 14:24 date
>> -rwxr-xr-x 1 0 0 51840 Feb 23 14:24 dd
>> -rwxr-xr-x 1 0 0 64208 Feb 23 14:24 df
>> -rwxr-xr-x 1 0 0 105776 Feb 23 14:24 dir
>> -rwxr-xr-x 1 0 0 26968 Feb 23 14:24 echo
>> -rwxr-xr-x 1 0 0 22856 Feb 23 14:24 false
>> -rwxr-xr-x 1 0 0 47680 Feb 23 14:24 ln
>> -rwxr-xr-x 1 0 0 105776 Feb 23 14:24 ls
>> -rwxr-xr-x 1 0 0 47624 Feb 23 14:24 mkdir
>> -rwxr-xr-x 1 0 0 31112 Feb 23 14:24 mknod
>> -rwxr-xr-x 1 0 0 35352 Feb 23 14:24 mktemp
>> -rwxr-xr-x 1 0 0 109584 Feb 23 14:24 mv
>> -rwxr-xr-x 1 0 0 31200 Feb 23 14:24 pwd
>> lrwxrwxrwx 1 0 0 4 Jul 20 21:19 rbash -> bash
>> -rwxr-xr-x 1 0 0 35272 Feb 23 14:24 readlink
>> -rwxr-xr-x 1 0 0 55872 Feb 23 14:24 rm
>> -rwxr-xr-x 1 0 0 39320 Feb 23 14:24 rmdir
>> -rwxr-xr-x 1 0 0 15048 Jan 20 2011 run-parts
>> lrwxrwxrwx 1 0 0 4 Jul 20 21:19 sh -> dash
>> -rwxr-xr-x 1 0 0 26984 Feb 23 14:24 sleep
>> -rwxr-xr-x 1 0 0 63992 Feb 23 14:24 stty
>> -rwxr-xr-x 1 0 0 22872 Feb 23 14:24 sync
>> -rwxr-xr-x 1 0 0 10312 Jan 20 2011 tempfile
>> -rwxr-xr-x 1 0 0 47640 Feb 23 14:24 touch
>> -rwxr-xr-x 1 0 0 22856 Feb 23 14:24 true
>> -rwxr-xr-x 1 0 0 27016 Feb 23 14:24 uname
>> -rwxr-xr-x 1 0 0 105776 Feb 23 14:24 vdir
>> -rwxr-xr-x 1 0 0 946 Jan 20 2011 which
>>
>> (The above output was from Ubuntu 11.04)
>>
>> Rich.
>>
>> --
>> Richard Jones, Virtualization Group, Red Hat
>> http://people.redhat.com/~rjones
>> libguestfs lets you edit virtual machines. Supports shell scripting,
>> bindings from many languages. http://libguestfs.org
>>
>
>
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