[PATCH 1/2] crypto: s5p - deal gracefully with bogus input sizes

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

The s5p skcipher driver returns -EINVAL for zero length inputs, which
deviates from the behavior of the generic ECB template, and causes fuzz
tests to fail. In cases where the input is not a multiple of the AES
block size (and the chaining mode is not CTR), it prints an error to
the kernel log, which is a thing we usually try to avoid in response
to situations that can be triggered by unprivileged users.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/crypto/s5p-sss.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/crypto/s5p-sss.c b/drivers/crypto/s5p-sss.c
index 9ef25230c199..ef90c58edb1f 100644
--- a/drivers/crypto/s5p-sss.c
+++ b/drivers/crypto/s5p-sss.c
@@ -2056,9 +2056,12 @@ static int s5p_aes_crypt(struct ablkcipher_request *req, unsigned long mode)
 	struct s5p_aes_ctx *ctx = crypto_ablkcipher_ctx(tfm);
 	struct s5p_aes_dev *dev = ctx->dev;
 
+	if (!req->nbytes)
+		return 0;
+
 	if (!IS_ALIGNED(req->nbytes, AES_BLOCK_SIZE) &&
 			((mode & FLAGS_AES_MODE_MASK) != FLAGS_AES_CTR)) {
-		dev_err(dev->dev, "request size is not exact amount of AES blocks\n");
+		dev_dbg(dev->dev, "request size is not exact amount of AES blocks\n");
 		return -EINVAL;
 	}
 
-- 
2.17.1