crypto: caam - Add check for kcalloc() in test_len()

As kcalloc() may fail, check its return value to avoid a NULL pointer
dereference when passing the buffer to rng->read(). On allocation
failure, log the error and return since test_len() returns void.

Fixes: 2be0d806e25e ("crypto: caam - add a test for the RNG")
Cc: [e-mail]
Signed-off-by: Guangshuo Li <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

drivers/crypto/caam/caamrng.c

···
 	struct device *dev = ctx->ctrldev;
 
 	buf = kcalloc(CAAM_RNG_MAX_FIFO_STORE_SIZE, sizeof(u8), GFP_KERNEL);
-
+	if (!buf) {
+		return;
+	}
 	while (len > 0) {
 		read_len = rng->read(rng, buf, len, wait);