OSSL_PROVIDER_unload() segfaults if called from external library destructor #15915
Description
We have to enable legacy provider in libcryptsetup for backward compatibility. Because we have support for various crypto backends, we have also a constructor (where we can load legacy provider) and destructor to unoad it.
The destructor is called from libcryptsetup exit handler automatically.
Unfortunately, it seems that OpenSSL cannot use OSSL_PROVIDER_* calls from this context.
Is it a bug or intentional feature?
Minimal example simulating this from simple C program:
#include <stdio.h>
#include <openssl/crypto.h>
#include <openssl/provider.h>
static OSSL_PROVIDER *ossl_legacy = NULL;
static OSSL_PROVIDER *ossl_default = NULL;
static void __attribute__((destructor)) my_exit(void)
{
printf("EXIT\n");
OSSL_PROVIDER_unload(ossl_legacy);
OSSL_PROVIDER_unload(ossl_default);
}
int main(int argc, char *argv[])
{
printf("OpenSSL (%s)\n", OpenSSL_version(OPENSSL_VERSION));
ossl_legacy = OSSL_PROVIDER_try_load(NULL, "legacy", 1);
ossl_default = OSSL_PROVIDER_try_load(NULL, "default", 1);
return 0;
}
Running that, I see:
OpenSSL (OpenSSL 3.0.0-beta1 17 Jun 2021)
EXIT
Program received signal SIGSEGV, Segmentation fault.
__GI___pthread_rwlock_rdlock (rwlock=0x0) at pthread_rwlock_rdlock.c:27
27 pthread_rwlock_rdlock.c: No such file or directory.
(gdb) bt
#0 __GI___pthread_rwlock_rdlock (rwlock=0x0) at pthread_rwlock_rdlock.c:27
#1 0x00007ffff7d65199 in CRYPTO_THREAD_read_lock () from /usr/lib/x86_64-linux-gnu/libcrypto.so.3
#2 0x00007ffff7d56327 in ?? () from /usr/lib/x86_64-linux-gnu/libcrypto.so.3
#3 0x00007ffff7d62149 in ?? () from /usr/lib/x86_64-linux-gnu/libcrypto.so.3
#4 0x00007ffff7d62fde in ?? () from /usr/lib/x86_64-linux-gnu/libcrypto.so.3
#5 0x00007ffff7d610a9 in OSSL_PROVIDER_unload () from /usr/lib/x86_64-linux-gnu/libcrypto.so.3
#6 0x000055555555519b in my_exit () at openssl-test.c:11
#7 0x00007ffff7fe2373 in _dl_fini () at dl-fini.c:138
#8 0x00007ffff79b44d7 in __run_exit_handlers (status=0, listp=0x7ffff7b34718 <__exit_funcs>, run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true) at exit.c:108
#9 0x00007ffff79b467a in __GI_exit (status=<optimized out>) at exit.c:139
#10 0x00007ffff799cd11 in __libc_start_main (main=0x5555555551ad <main>, argc=1, argv=0x7fffffffe188, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffe178) at ../csu/libc-start.c:342
#11 0x00005555555550ba in _start ()