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

commit 7cf6e0b upstream.

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: 2be0d80 ("crypto: caam - add a test for the RNG")
Cc: stable@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: lgs2513

drivers/crypto/caam/caamrng.c

@@ -181,7 +181,9 @@ static inline void test_len(struct hwrng *rng, size_t len, bool wait)
 	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);