[PATCH v5 7/7] crypto: qce - Use fallback for CCM with a fragmented payload

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

The crypto engine reliably processes CCM only when the message payload
is a single contiguous buffer. The associated data is already linearized
into a bounce buffer before being submitted, but when the payload itself
is split across multiple scatterlist entries the engine stalls waiting
for input and the request fails 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, skipping past the associated data) and
route the request to the software fallback.

Cc: stable@vger.kernel.org
Fixes: 9363efb4181c ("crypto: qce - Add support for AEAD algorithms")
Tested-by: Kuldeep Singh <kuldeep.singh@oss.qualcomm.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
---
 drivers/crypto/qce/aead.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/crypto/qce/aead.c b/drivers/crypto/qce/aead.c
index 4fa018204cb628c112f64c45ff6c7407df73b945..9ff8fe2a7efcd2734e4ff029744961a7b1101013 100644
--- a/drivers/crypto/qce/aead.c
+++ b/drivers/crypto/qce/aead.c
@@ -498,7 +498,8 @@ static int qce_aead_crypt(struct aead_request *req, int encrypt)
 	struct qce_aead_reqctx *rctx = aead_request_ctx_dma(req);
 	struct qce_aead_ctx *ctx = crypto_aead_ctx(tfm);
 	struct qce_alg_template *tmpl = to_aead_tmpl(tfm);
-	unsigned int blocksize = crypto_aead_blocksize(tfm);
+	unsigned int blocksize = crypto_aead_blocksize(tfm), authsize;
+	struct scatterlist __sg[2], *msg_sg;
 
 	rctx->flags  = tmpl->alg_flags;
 	rctx->flags |= encrypt ? QCE_ENCRYPT : QCE_DECRYPT;
@@ -522,6 +523,27 @@ static int qce_aead_crypt(struct aead_request *req, int encrypt)
 	if (IS_CCM(rctx->flags) && !IS_ALIGNED(rctx->cryptlen, AES_BLOCK_SIZE))
 		ctx->need_fallback = true;
 
+	/*
+	 * The CE reliably processes CCM only when the message payload is a
+	 * single contiguous buffer. The associated data is linearized into a
+	 * bounce buffer before being handed to the engine, but a fragmented
+	 * payload makes the engine stall waiting for input, so route those
+	 * requests to the fallback.
+	 */
+	if (IS_CCM(rctx->flags) && rctx->cryptlen) {
+		authsize = ctx->authsize;
+
+		msg_sg = scatterwalk_ffwd(__sg, req->src, req->assoclen);
+		if (sg_nents_for_len(msg_sg, rctx->cryptlen +
+				     (encrypt ? 0 : authsize)) > 1)
+			ctx->need_fallback = true;
+
+		msg_sg = scatterwalk_ffwd(__sg, req->dst, req->assoclen);
+		if (sg_nents_for_len(msg_sg, rctx->cryptlen +
+				     (encrypt ? authsize : 0)) > 1)
+			ctx->need_fallback = true;
+	}
+
 	/* If fallback is needed, schedule and exit */
 	if (ctx->need_fallback) {
 		/* Reset need_fallback in case the same ctx is used for another transaction */

-- 
2.47.3