Hardy regression: glibc 2.7-9ubuntu1 NSS module broken due to toolchain changes

Colin Watson cjwatson at ubuntu.com
Thu Mar 13 15:49:35 GMT 2008


This bug affects the Hardy development release (to become Ubuntu 8.04
LTS) ONLY. Stable releases of Ubuntu are NOT affected.

In glibc 2.7-9ubuntu1, many critical programs (such as bash and sudo)
fail to run with various error messages, such as "malloc:
../bash/subst.c:3472: assertion botched" from bash and "*** glibc
detected *** sudo: free(): invalid pointer: 0xb7fabb70 ***" from sudo.
This renders the system unusable. This bug was introduced due to changes
in the default value of LDFLAGS for package builds; while these changes
were useful and had been tested elsewhere, they unexpectedly broke the C
library when it was next built.

The quickest workaround is to copy an older version of the C library
from the initramfs. This will work provided you upgraded from a
relatively recent version of Hardy, so that the initramfs really does
have an older version. DO NOT do this if you encountered this bug
immediately after upgrading from Ubuntu 7.10 or earlier, as it will
break your system badly. Reboot if necessary, and follow these steps:

 * Press Escape at start-up time to access the GRUB menu (this is not
   necessary on all systems)
 * Press 'e' to edit the normal Ubuntu boot options
 * Use the cursor keys to reach the line starting with 'kernel'
 * Press 'e' again to edit the boot command line
 * Change 'ro' to 'rw', remove 'splash', and add 'break=bottom' (without
   the quotes) to the end of the boot options
 * Press Enter and then 'b' to start up
 * After a few moments, you will be presented with an '(initramfs)'
 * Type the following (you may see some 'No such file or directory'
   messages after running the cp command, which you can safely ignore):
     mount -o remount,rw /root
     cp /lib/libc.so.6 /lib/libdl.so.2 /lib/libm.so.6 /lib/libpthread.so.0 /lib/librt.so.1 /root/lib/
     # run the following on the 32-bit PC edition (i386)
     cp /lib/ld-linux.so.2 /root/lib/
     # run the following on the 64-bit PC edition (amd64)
     cp /lib64/ld-linux-x86-64.so.2 /root/lib64/
     umount /root
 * Start up normally

If this does not work, or if you encountered this bug immediately after
upgrading from Ubuntu 7.10 or earlier, then you will need to follow the
steps below instead.

If you have turned off your system, then you will be unable to start up
and log in normally. In that case, get hold of a Hardy Alpha 6 desktop
CD (since you are running a development version of Ubuntu, this should
be reasonable); you can download it from
http://cdimage.ubuntu.com/releases/hardy/alpha-6/ if you do not have one
to hand, and follow these steps:

 * Start up from the desktop CD
 * Run Applications -> Accessories -> Terminal (GNOME) or K-Menu ->
   System -> Konsole (KDE)

 * If you are running the 32-bit PC (i386) edition of Ubuntu, type the
   following into the terminal window:
     wget http://launchpadlibrarian.net/11110565/libc6_2.7-5ubuntu2_i386.deb
 * If you are running the 64-bit PC (amd64) edition of Ubuntu, type the
   following into the terminal window:
     wget http://launchpadlibrarian.net/11109997/libc6_2.7-5ubuntu2_amd64.deb
 * If you are running some other edition of Ubuntu, older packages may
   be available from http://archive.ubuntu.com/ubuntu/pool/main/g/glibc/

 * In any case, continue by finding out the device name for your root
   partition, which will look something like '/dev/sda1'. You can run
   'sudo fdisk -l' to find out all the available device names. The one
   you want will have 'Linux' in the 'System' column. A default
   installation will only have one such device; if you have more than
   one, then you probably know what you are doing!
 * Type the following into the terminal window, replacing DEVICE with
   the device name you found above:
     sudo mount DEVICE /mnt
     sudo mount --bind /dev /mnt/dev
     sudo mount --bind /proc /mnt/proc
     sudo cp libc6_*.deb /mnt/tmp/
     # replace 'i386' with 'amd64' if you are running the 64-bit PC edition
     sudo chroot /mnt dpkg -i /tmp/libc6_2.7-5ubuntu2_i386.deb
     # this step may return some errors; don't worry about them
     sudo chroot /mnt dpkg --configure -a
     sudo umount /mnt/proc
     sudo umount /mnt/dev
     sudo umount /mnt
 * Reboot

Fixed packages (version 2.7-9ubuntu2) are now on archive.ubuntu.com.
However, many mirrors will not yet have picked this up, so we advise
that you be careful about upgrades for the next couple of days to avoid
reintroducing the bug.

Colin Watson                                       [cjwatson at ubuntu.com]
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