Created attachment 462378 [details]
Proposed patch.

Description of problem:

If you use file -s on some block device types (namely LUKS and LVM devices), reported UUID is truncated (and it leads to various false reports).

Version-Release number of selected component (if applicable):
file-5.04-15.fc15.x86_64

Steps to Reproduce:
Simple create these devices types and compare UUID with blkid:

# dd if=/dev/zero of=tst bs=1M count=64
# losetup /dev/loop7 tst

# echo "password" | cryptsetup luksFormat /dev/loop7
# blkid -p /dev/loop7
/dev/loop7: UUID="da48f0ff-a262-4ad6-a285-6d49152d5aab" VERSION="1" TYPE="crypto_LUKS" USAGE="crypto" 

# file -s /dev/loop7
/dev/loop7: LUKS encrypted file, ver 1 [aes, cbc-essiv:sha256, sha1] UUID: da48f0ff-a262-4ad6-a285-6d49152

Note missing "d5aab" suffix in UUID

The same for LVM PV:

# pvcreate /dev/loop7
  Physical volume "/dev/loop7" successfully created

# blkid -p /dev/loop7
/dev/loop7: UUID="lWwCD3-ykbN-3Tmp-y32N-jS7Z-cMGf-M61338" VERSION="LVM2 001" TYPE="LVM2_member" USAGE="raid" 

# file -s /dev/loop7
/dev/loop7: LVM2 (Linux Logical Volume Manager) , UUID: lWwCD3ykbN3Tmpy32NjS7ZcMGfM6133

Missing "8" in UUID.

Expected results:

Proper UUID report;-)

Additional info:

Attached patch fixes it for me by increasing internal string limit but not sure if there are some side effects (magic file compatibility?).