[PATCH v11 3/4] crypto: qce - Use fallback for fragmented skcipher payloads

[Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>]

The crypto engine reliably processes AES requests only when the payload
is a single contiguous buffer. A payload split across multiple
scatterlist entries makes the engine stall waiting for input, failing
the request with a hardware operation error. This was uncovered by the
crypto self-tests, which feed the algorithms randomly fragmented
buffers.

Detect a payload that spans more than one scatterlist entry, in either
the source or the destination, and route the request to the software
fallback.

Cc: stable@vger.kernel.org
Fixes: 25b71d61d631 ("crypto: qce - Improve the conditions for requesting AES fallback cipher")
Tested-by: Kuldeep Singh <kuldeep.singh@oss.qualcomm.com>
Tested-by: Pankaj Patil <pankaj.patil@oss.qualcomm.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
---
 drivers/crypto/qce/cipher.h   |  1 +
 drivers/crypto/qce/skcipher.c | 13 +++++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/qce/cipher.h b/drivers/crypto/qce/cipher.h
index 850f257d00f3aca0397adc1f703aea690c754d60..daea07551118d444d2f749588bdfe2ae2c6c553f 100644
--- a/drivers/crypto/qce/cipher.h
+++ b/drivers/crypto/qce/cipher.h
@@ -14,6 +14,7 @@
 struct qce_cipher_ctx {
 	u8 enc_key[QCE_MAX_KEY_SIZE];
 	unsigned int enc_keylen;
+	bool use_fallback;
 	struct crypto_skcipher *fallback;
 };
 
diff --git a/drivers/crypto/qce/skcipher.c b/drivers/crypto/qce/skcipher.c
index c23ebc61873f1c542a4b475904c3c3a3d89bcc35..0473033db2af90e119b731b9a6ec96de5973d3c8 100644
--- a/drivers/crypto/qce/skcipher.c
+++ b/drivers/crypto/qce/skcipher.c
@@ -215,7 +215,7 @@ static int qce_skcipher_crypt(struct skcipher_request *req, int encrypt)
 	struct qce_cipher_reqctx *rctx = skcipher_request_ctx(req);
 	struct qce_alg_template *tmpl = to_cipher_tmpl(tfm);
 	unsigned int blocksize = crypto_skcipher_blocksize(tfm);
-	int keylen;
+	int keylen, src_nents, dst_nents;
 
 	rctx->flags = tmpl->alg_flags;
 	rctx->flags |= encrypt ? QCE_ENCRYPT : QCE_DECRYPT;
@@ -237,6 +237,11 @@ static int qce_skcipher_crypt(struct skcipher_request *req, int encrypt)
 		if (!IS_ALIGNED(req->cryptlen, blocksize))
 			return -EINVAL;
 
+	src_nents = sg_nents_for_len(req->src, req->cryptlen);
+	dst_nents = sg_nents_for_len(req->dst, req->cryptlen);
+	if (src_nents < 0 || dst_nents < 0)
+		return -EINVAL;
+
 	/*
 	 * Conditions for requesting a fallback cipher
 	 * AES-192 (not supported by crypto engine (CE))
@@ -246,13 +251,17 @@ static int qce_skcipher_crypt(struct skcipher_request *req, int encrypt)
 	 * needed in all versions of CE)
 	 * AES-CTR with a partial final block (the CE stalls waiting for a full
 	 * block of input).
+	 * A payload fragmented across more than one scatterlist entry (the CE
+	 * stalls waiting for input in that case too).
 	 */
 	if (IS_AES(rctx->flags) &&
 	    ((keylen != AES_KEYSIZE_128 && keylen != AES_KEYSIZE_256) ||
 	    (IS_CTR(rctx->flags) && !IS_ALIGNED(req->cryptlen, AES_BLOCK_SIZE)) ||
 	    (IS_XTS(rctx->flags) && ((req->cryptlen <= aes_sw_max_len) ||
 	    (req->cryptlen > QCE_SECTOR_SIZE &&
-	    req->cryptlen % QCE_SECTOR_SIZE))))) {
+	    req->cryptlen % QCE_SECTOR_SIZE))) ||
+	    (IS_XTS(rctx->flags) && ctx->use_fallback) ||
+	    src_nents > 1 || dst_nents > 1)) {
 		skcipher_request_set_tfm(&rctx->fallback_req, ctx->fallback);
 		skcipher_request_set_callback(&rctx->fallback_req,
 					      req->base.flags,

-- 
2.47.3