[PATCH v12 1/4] crypto: qce - Reject messages shorter than a block for AES-XTS

[Bartosz Golaszewski]

XTS is not defined for a payload shorter than one cipher block. The
driver treated a zero-length request as a successful no-op, so the
crypto self-tests "unexpectedly succeeded" when -EINVAL was expected.
Requests of 1 to 15 bytes are not rejected either and, when they are not
diverted to the fallback (e.g. with aes_sw_max_len set to 0), reach the
engine which stalls waiting for a full block of input.

Return -EINVAL for XTS requests shorter than AES_BLOCK_SIZE while
keeping the no-op behavior for empty requests of the other ciphers,
which the crypto engine simply cannot process due to its DMA not
supporting zero-length transfers.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: f08789462255 ("crypto: qce - Return error for zero length messages")
Tested-by: Kuldeep Singh <kuldeep.singh@xxxxxxxxxxxxxxxx>
Tested-by: Pankaj Patil <pankaj.patil@xxxxxxxxxxxxxxxx>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
---
 drivers/crypto/qce/skcipher.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/crypto/qce/skcipher.c b/drivers/crypto/qce/skcipher.c
index 03a3cec2bb90e8d8c17e491ca40ec740a003d1b4..d9a5b255015341e741515bdfd6ff54bd3b24f1e3 100644
--- a/drivers/crypto/qce/skcipher.c
+++ b/drivers/crypto/qce/skcipher.c
@@ -221,6 +221,14 @@ static int qce_skcipher_crypt(struct skcipher_request *req, int encrypt)
 	rctx->flags |= encrypt ? QCE_ENCRYPT : QCE_DECRYPT;
 	keylen = IS_XTS(rctx->flags) ? ctx->enc_keylen >> 1 : ctx->enc_keylen;
 
+	/*
+	 * XTS requires at least one full block of data. Reject anything
+	 * shorter here as the engine would stall waiting for more input if
+	 * such a request reached it.
+	 */
+	if (IS_XTS(rctx->flags) && req->cryptlen < AES_BLOCK_SIZE)
+		return -EINVAL;
+
 	/* CE does not handle 0 length messages */
 	if (!req->cryptlen)
 		return 0;

-- 
2.47.3