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Delete |pthread_key_t| on dlclose.

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When OPENSSL_DANGEROUS_RELEASE_PTHREAD_KEY is defined during the build,
this change adds a destructor function that is called when BoringSSL is
unloaded via |dlclose| or during process exit. Using |dlclose| with
BoringSSL is not supported and will leak memory, but this change allows
some code that is already doing it to survive longer.

Change-Id: Ifc6d6aae61ed0f15d61cd3dbb4ea9f8006e43dba
Reviewed-on: https://boringssl-review.googlesource.com/25784
Reviewed-by: Adam Langley <agl@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Reviewed-by: Fred Gylys-Colwell <fredgc@google.com>
This commit is contained in:
Fred Gylys-Colwell 2018-02-07 17:11:18 -08:00 committed by Adam Langley
parent ed626ec99b
commit 02d696f2a1
1 changed files with 35 additions and 5 deletions
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40
crypto/thread_pthread.c
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@ -94,6 +94,8 @@ void CRYPTO_once(CRYPTO_once_t *once, void (*init)(void)) {
static pthread_mutex_t g_destructors_lock = PTHREAD_MUTEX_INITIALIZER;
static thread_local_destructor_t g_destructors[NUM_OPENSSL_THREAD_LOCALS];
// thread_local_destructor is called when a thread exits. It releases thread
// local data for that thread only.
static void thread_local_destructor(void *arg) {
if (arg == NULL) {
return;
@ -119,16 +121,44 @@ static void thread_local_destructor(void *arg) {
static pthread_once_t g_thread_local_init_once = PTHREAD_ONCE_INIT;
static pthread_key_t g_thread_local_key;
static int g_thread_local_failed = 0;
static int g_thread_local_key_created = 0;
// OPENSSL_DANGEROUS_RELEASE_PTHREAD_KEY can be defined to cause
// |pthread_key_delete| to be called in a destructor function. This can be
// useful for programs that dlclose BoringSSL.
//
// Note that dlclose()ing BoringSSL is not supported and will leak memory:
// thread-local values will be leaked as well as anything initialised via a
// once. The |pthread_key_t| is destroyed because they run out very quickly,
// while the other leaks are slow, and this allows code that happens to use
// dlclose() despite all the problems to continue functioning.
//
// This is marked "dangerous" because it can cause multi-threaded processes to
// crash (even if they don't use dlclose): if the destructor runs while other
// threads are still executing then they may end up using an invalid key to
// access thread-local variables.
//
// This may be removed after February 2020.
#if defined(OPENSSL_DANGEROUS_RELEASE_PTHREAD_KEY) && \
(defined(__GNUC__) || defined(__clang__))
// thread_key_destructor is called when the library is unloaded with dlclose.
static void thread_key_destructor(void) __attribute__((destructor, unused));
static void thread_key_destructor(void) {
if (g_thread_local_key_created) {
g_thread_local_key_created = 0;
pthread_key_delete(g_thread_local_key);
}
}
#endif
static void thread_local_init(void) {
g_thread_local_failed =
pthread_key_create(&g_thread_local_key, thread_local_destructor) != 0;
g_thread_local_key_created =
pthread_key_create(&g_thread_local_key, thread_local_destructor) == 0;
}
void *CRYPTO_get_thread_local(thread_local_data_t index) {
CRYPTO_once(&g_thread_local_init_once, thread_local_init);
if (g_thread_local_failed) {
if (!g_thread_local_key_created) {
return NULL;
}
@ -142,7 +172,7 @@ void *CRYPTO_get_thread_local(thread_local_data_t index) {
int CRYPTO_set_thread_local(thread_local_data_t index, void *value,
thread_local_destructor_t destructor) {
CRYPTO_once(&g_thread_local_init_once, thread_local_init);
if (g_thread_local_failed) {
if (!g_thread_local_key_created) {
destructor(value);
return 0;
}