crypto: krb5 - Fix memory leak in krb5_test_one_prf()

Fix a leak reported by kmemleak:

    unreferenced object 0xffff8880093bf7a0 (size 32):
      comm "swapper/0", pid 1, jiffies 4294877529
      hex dump (first 32 bytes):
        9d 18 86 16 f6 38 52 fe 86 91 5b b8 40 b4 a8 86  .....8R...[.@...
        ff 3e 6b b0 f8 19 b4 9b 89 33 93 d3 93 85 42 95  .>k......3....B.
      backtrace (crc 8ba12f3b):
        kmemleak_alloc+0x8d/0xa0
        __kmalloc_noprof+0x3cd/0x4d0
        prep_buf+0x36/0x70
        load_buf+0x10d/0x1c0
        krb5_test_one_prf+0x1e1/0x3c0
        krb5_selftest.cold+0x7c/0x54c
        crypto_krb5_init+0xd/0x20
        do_one_initcall+0xa5/0x230
        do_initcalls+0x213/0x250
        kernel_init_freeable+0x220/0x260
        kernel_init+0x1d/0x170
        ret_from_fork+0x301/0x410
        ret_from_fork_asm+0x1a/0x30

Fixes: fc0cf10 ("crypto/krb5: Implement crypto self-testing")
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: Eric Biggers

crypto/krb5/selftest.c

@@ -152,6 +152,7 @@ static int krb5_test_one_prf(const struct krb5_prf_test *test)
 
 out:
 	clear_buf(&result);
+	clear_buf(&prf);
 	clear_buf(&octet);
 	clear_buf(&key);
 	return ret;