[PATCH v2] crypto: tegra - fix rctx->cryptlen calculation in tegra_gcm_do_one_req()

[Vladislav Dronov <vdronov@redhat.com>]

Perform rctx->cryptlen calculation in tegra_gcm_do_one_req() the same way
it is done in tegra_ccm_crypt_init(). The current formulae may lead to a
crash if a caller does not call tegra_gcm_setauthsize() and so ctx->authsize
remains zero. Then a decrypt operation with incorrect rctx->cryptlen will
lead to a write beyound rctx->dst_sg buffer.

As a follow-up cleanup delete struct tegra_aead_ctx->authsize field since
it appears to be completely unused. Also simplify tegra_ccm_setauthsize()
and tegra_gcm_setauthsize() functions respectively.

Fixes: 0880bb3b00c8 ("crypto: tegra - Add Tegra Security Engine driver")
Signed-off-by: Vladislav Dronov <vdronov@redhat.com>
---
 drivers/crypto/tegra/tegra-se-aes.c | 22 +++-------------------
 1 file changed, 3 insertions(+), 19 deletions(-)

diff --git a/drivers/crypto/tegra/tegra-se-aes.c b/drivers/crypto/tegra/tegra-se-aes.c
index 9094c03e991f6..0fd1d70358996 100644
--- a/drivers/crypto/tegra/tegra-se-aes.c
+++ b/drivers/crypto/tegra/tegra-se-aes.c
@@ -45,7 +45,6 @@ struct tegra_aes_reqctx {
 
 struct tegra_aead_ctx {
 	struct tegra_se *se;
-	unsigned int authsize;
 	u32 alg;
 	u32 key_id;
 	u32 keylen;
@@ -1290,7 +1289,7 @@ static int tegra_gcm_do_one_req(struct crypto_engine *engine, void *areq)
 	if (rctx->encrypt)
 		rctx->cryptlen = req->cryptlen;
 	else
-		rctx->cryptlen = req->cryptlen - ctx->authsize;
+		rctx->cryptlen = req->cryptlen - rctx->authsize;
 
 	memcpy(rctx->iv, req->iv, GCM_AES_IV_SIZE);
 	rctx->iv[3] = (1 << 24);
@@ -1394,8 +1393,6 @@ static int tegra_aead_cra_init(struct crypto_aead *tfm)
 
 static int tegra_ccm_setauthsize(struct crypto_aead *tfm,  unsigned int authsize)
 {
-	struct tegra_aead_ctx *ctx = crypto_aead_ctx(tfm);
-
 	switch (authsize) {
 	case 4:
 	case 6:
@@ -1404,28 +1401,15 @@ static int tegra_ccm_setauthsize(struct crypto_aead *tfm,  unsigned int authsize
 	case 12:
 	case 14:
 	case 16:
-		break;
+		return 0;
 	default:
 		return -EINVAL;
 	}
-
-	ctx->authsize = authsize;
-
-	return 0;
 }
 
 static int tegra_gcm_setauthsize(struct crypto_aead *tfm,  unsigned int authsize)
 {
-	struct tegra_aead_ctx *ctx = crypto_aead_ctx(tfm);
-	int ret;
-
-	ret = crypto_gcm_check_authsize(authsize);
-	if (ret)
-		return ret;
-
-	ctx->authsize = authsize;
-
-	return 0;
+	return crypto_gcm_check_authsize(authsize);
 }
 
 static void tegra_aead_cra_exit(struct crypto_aead *tfm)
-- 
2.47.3