From 5836780f436e03be231ff245f04f2f9f2f0ede91 Mon Sep 17 00:00:00 2001 From: Matt Caswell Date: Tue, 18 Oct 2016 14:13:25 +0100 Subject: [PATCH] Ensure that libcrypto and libssl do not unload until the process exits Because we use atexit() to cleanup after ourselves, this will cause a problem if we have been dynamically loaded and then unloaded again: the atexit() handler may no longer be there. Most modern atexit() implementations can handle this, however there are still difficulties if libssl gets unloaded before libcrypto, because of the atexit() callback that libcrypto makes to libssl. The most robust solution seems to be to ensure that libcrypto and libssl never unload. This is done by simply deliberately leaking a dlopen() reference to them. Reviewed-by: Tim Hudson --- crypto/init.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/crypto/init.c b/crypto/init.c index 93ec7bbc69..ebc41465d5 100644 --- a/crypto/init.c +++ b/crypto/init.c @@ -23,6 +23,7 @@ #include #include #include +#include static int stopped = 0; @@ -79,6 +80,18 @@ DEFINE_RUN_ONCE_STATIC(ossl_init_base) return 0; OPENSSL_cpuid_setup(); base_inited = 1; + + /* + * Deliberately leak a reference to ourselves. This will force the library + * to remain loaded until the atexit() handler is run a process exit. + */ + { + DSO *dso = NULL; + + dso = DSO_dsobyaddr(&base_inited, DSO_FLAG_NO_UNLOAD_ON_FREE); + DSO_free(dso); + } + return 1; } @@ -575,6 +588,24 @@ int OPENSSL_atexit(void (*handler)(void)) { OPENSSL_INIT_STOP *newhand; + /* + * Deliberately leak a reference to the handler. This will force the + * library/code containing the handler to remain loaded until we run the + * atexit handler. + */ + { + DSO *dso = NULL; + union { + void *sym; + void (*func)(void); + } handlersym; + + handlersym.func = handler; + + dso = DSO_dsobyaddr(handlersym.sym, DSO_FLAG_NO_UNLOAD_ON_FREE); + DSO_free(dso); + } + newhand = OPENSSL_malloc(sizeof(*newhand)); if (newhand == NULL) return 0; -- 2.34.1