mmap_cache: Skip records which doesn't have same hash

The code uses 2 hashes for each record, but only one hash table to
index them both, furthermore each record has only one single 'next'
pointer.

This means that in certain conditions a record main end up being on a
hash chain even though its hashes do not match the hash chain. This can
happen when another record 'drags' it in from another hash chain where
they both belong.

If the record without matching hashes happens to be the second of the
chain and the first record is removed, then the non matching record is
left on the wrong chain. On removal of the non-matching record the hash
chain will not be updated and the hash chain will end up pointing to an
invalid slot.
This slot may be later reused for another record and may not be the
first slot of this new record. In this case the hash chain will point to
arbitrary data and may cause issues if the slot is interpreted as the
head of a record.

By skipping any block that has no matching hashes upon removing the
first record in a chain we insure that dangling references cannot be
left in the hash table

Resolves:
https://fedorahosted.org/sssd/ticket/2049

0 files changed, 0 insertions, 0 deletions