[Python-Dev] OpenSSL thread safety when reading files? (original) (raw)

Bill Janssen janssen at parc.com
Fri Sep 7 23:53:36 CEST 2007

I'm seeing a number of malloc (actully, free) errors, now that I'm pounding on the OpenSSL server/client setup with lots of server threads and client threads. They all look like either

(gdb) bt #0 0x9010b807 in malloc_printf () #1 0x900058ad in szone_free () #2 0x90005588 in free () #3 0x9194e508 in CRYPTO_free () #4 0x91993e77 in ERR_clear_error () #5 0x919b1884 in PEM_X509_INFO_read_bio () #6 0x9197a692 in X509_load_cert_crl_file () #7 0x9197a80e in by_file_ctrl () #8 0x919d6e2e in X509_STORE_load_locations () [...]

or (much more frequently)

(gdb) bt #0 0x9010b807 in malloc_printf () #1 0x900058ad in szone_free () #2 0x90005588 in free () #3 0x9194e508 in CRYPTO_free () #4 0x91993e77 in ERR_clear_error () #5 0x949fcf11 in SSL_CTX_use_certificate_chain_file () [...]

Always in ERR_clear_error(), always from some frame that's reading a certificate file for some purpose.

If I disable Py_BEGIN_ALLOW_THREADS/Py_END_ALLOW_THREADS around the places where the C code reads the certificate files, all these free errors go away.

ERR_clear_error() is supposed to be thread-safe; it operates on a per-thread error state structure (which I make sure is initialized in my C code). But it sure looks like the client and server threads are both working with the same error state.

Bill

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