fs/xfs: Fix out-of-bounds read

fs/xfs: Fix out-of-bounds read

The number of records in the root key array read from disk was not being
validated against the size of the root node. This could lead to an
out-of-bounds read.

This patch adds a check to ensure that the number of records in the root
key array does not exceed the expected size of a root node read from
disk. If this check detects an out-of-bounds condition the operation is
aborted to prevent random errors due to metadata corruption.

Reported-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Michael Chang <mchang@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>