DBI versions before 1.656 for Perl crash via type confusion in dbi_profile when a database handle is destroyed under a Profile Path with an {attr} element

DBI versions before 1.656 for Perl crash via type confusion in dbi_profile when a database handle is destroyed under a Profile Path with an {attr} element.

An {attr} element names a database handle attribute, which dbi_profile reads from the handle's inner hash. It expects the inner handle as a reference and dereferences it, but a handle that is being destroyed hands back the inner hash itself, so the dereference yields the hash's bucket array. A type check on that pointer usually fails and the call goes unprofiled. When the memory it addresses passes the check, the attribute lookup dereferences a NULL or invalid pointer and the process dies on SIGSEGV.

The Path is set by the application, by the Profile handle attribute, or by the DBI_PROFILE environment variable, so `DBI_PROFILE={ImplementorClass}` can crash an unmodified program.