Segmentation Fault in EVP_DigestFinal_ex -> SHA256_Final due to NULL algctx - hash

Question

using Linux (ubuntu 20.04) machine, openssl 3.0.7 is installed , running a sample code for signing.
we followed below procedure for signing. getting segmentation fault in EVP_DigestFinal_ex.
segmentation fault is happening due to mdctx->algctx=0x0. while debugging the code mdctx->algctx is updated in EVP_DigestInit_ex but latter it was freed in EVP_DigestSignInit. not sure what we are missing and how to update mdctx->algctx to avoid the crash.
#include <stdio.h>
#include <string.h>
#include <openssl/evp.h>
#include <openssl/provider.h>
EVP_PKEY *pkey = NULL;
generate_key(){
EVP_PKEY_CTX *ctx=NULL;
pkey=EVP_PKEY_new();
ctx=EVP_PKEY_CTX_new(pkey,NULL);
ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, NULL);
if (!ctx)
printf(" key gen failed");
if (EVP_PKEY_keygen_init(ctx) <= 0)
printf(" key gen failed");
if (EVP_PKEY_CTX_set_rsa_keygen_bits(ctx, 512) <= 0)
printf(" key gen failed");
/* Generate key */
if (EVP_PKEY_keygen(ctx, &pkey) <= 0)
printf(" key gen failed");
}
int main(int argc, char *argv[])
{
EVP_MD_CTX *mdctx;
const EVP_MD *m_md;
const EVP_MD *md;
EVP_PKEY *m_key;
EVP_PKEY *ed_pkey = NULL;
EVP_PKEY_CTX *ed_pctx = NULL;
// OSSL_PROVIDER *default;
size_t sign_len = 0;
u_int8_t m_sign_buf[2048];
int ret = 0;
char mess1[] = "Test Message\n";
char mess2[] = "Hello World\n";
unsigned char *outdigest = NULL;
unsigned int md_len = 0, i;
printf("args : %s\n",argv[1]);
//default = OSSL_PROVIDE_load(NULL, "default");
//md = EVP_get_digestbyname("SHA256");
//md = EVP_sha256();
md = EVP_MD_fetch(NULL, "SHA256", NULL); //;
if (md == NULL) {
printf("Unknown message digest %s\n", argv[1]);
exit(1);
}
generate_key();
printf("value of md %s\n",md);
mdctx = EVP_MD_CTX_new();
if((EVP_DigestInit_ex(mdctx, md, NULL)) != 1)
printf("EVP_DigestInit_ex failed \n");
if((EVP_DigestSignInit(mdctx, NULL, md, NULL, pkey)) != 1)
printf("EVP_DigestSignInit failed \n");
if((EVP_DigestSignUpdate(mdctx, mess1, strlen(mess1))) != 1)
printf("EVP_DigestSignUpdate failed \n");
//EVP_DigestUpdate(mdctx, mess2, strlen(mess2));
if((EVP_DigestSignFinal(mdctx, (u_int8_t*)NULL, &sign_len)) != 1)
printf("EVP_DigestSignFinal failed \n");
if((EVP_DigestSignFinal(mdctx, m_sign_buf, &sign_len)) != 1)
printf("EVP_DigestSignFinal 2 failed \n");
/* Allocate the output buffer */
outdigest = OPENSSL_malloc(EVP_MD_get_size(md));
if (outdigest == NULL)
printf("outdigest failed \n");
if((EVP_DigestFinal_ex(mdctx, outdigest, &md_len)) != 1)
printf("EVP_DigestFinal_ex failed \n");
EVP_MD_CTX_free(mdctx);
/* Print out the digest result */
BIO_dump_fp(stdout, outdigest, &md_len);
exit(0);
}
`
```
Thanks,
while debugging the code mdctx->algctx is updated in EVP_DigestInit_ex but latter it was freed in EVP_DigestSignInit. not sure what we are missing and how to update mdctx->algctx to avoid the crash.
CRASH Info:
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7d99422 in SHA256_Final (md=0x5555555a88d0 "\250UUU\005", c=0x0)
    at ../openssl-3.0.7/include/crypto/md32_common.h:194
194         size_t n = c->num;
(gdb) bt
#0  0x00007ffff7d99422 in SHA256_Final (md=0x5555555a88d0 "\250UUU\005", c=0x0)
    at ../openssl-3.0.7/include/crypto/md32_common.h:194
#1  0x00007ffff7e2628c in sha256_internal_final (ctx=0x0, out=0x5555555a88d0 "\250UUU\005", outl=0x7fffffffda98,
    outsz=32) at ../openssl-3.0.7/providers/implementations/digests/sha2_prov.c:72
#2  0x00007ffff7cbadf6 in EVP_DigestFinal_ex (ctx=0x555555580d80, md=0x5555555a88d0 "\250UUU\005",
    isize=0x7fffffffdad8) at ../openssl-3.0.7/crypto/evp/digest.c:446
#3  0x000055555555575f in main (argc=1, argv=0x7fffffffe458) at test2.c:90