Because no lock was held while comparing the type of the already stored
cache entry, it was theoretically possible that a NULL-pointer dereference
or use-after-free was caused if another thread concurrently replaced the
stored certificate.
While the cached type is also read without lock, the worst that can
happen is that we acquire the lock of an entry that doesn't match
eventually. The double check actually uses the stored certificate,
just in case the cached value gets out of sync due to a future
refactoring.
Fixes: 2271ebb325 ("Newer CRLs replace older versions of the CRL in the cache")
Fixes: 47e8b21c76 ("cert_cache: Replace cached stale OCSP responses in-place")
Tobias Brunner
87f0bc2a6c