I'm running 2.2.17pre12 with crypto patch 16.4.
It seems that the decrypted data from a loop device is cached between
destroys and new setups of loop devices. You cannot see this if you just
mount the loop devices because mount seems unaffected, but fsck will
show the error.
Attached is an example session.
This is a security problem because users can see decrypted data even
after the loop device was destroyed (imagine a setuid application which
allows users to mount their own encrypted file systems).
Example:
frodo:/home/wh # /usr/local/bin/losetup -e serpent /dev/loop0 /usr/local/loop/wh
Password : wrong password
frodo:/home/wh # mount -t ext2 /dev/loop0 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
or too many mounted file systems
frodo:/home/wh # /usr/local/bin/losetup -d /dev/loop0
frodo:/home/wh # /usr/local/bin/losetup -e serpent /dev/loop0 /usr/local/loop/wh
Password : correct password
frodo:/home/wh # /sbin/e2fsck /dev/loop0
e2fsck 1.18, 11-Nov-1999 for EXT2 FS 0.5b, 95/08/09
Group descriptors look bad... trying backup blocks...
/sbin/e2fsck: Bad magic number in super-block while trying to open /dev/loop0
The superblock could not be read or does not describe a correct ext2
filesystem. If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
e2fsck -b 8193 <device>
frodo:/home/wh # mount /dev/loop0 /mnt
frodo:/home/wh # umount /mnt
frodo:/home/wh # /sbin/e2fsck /dev/loop0
e2fsck 1.18, 11-Nov-1999 for EXT2 FS 0.5b, 95/08/09
/dev/loop0: clean, 4650/81920 files, 66139/163840 blocks
Walter
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