FAILED: patch "[PATCH] crypto: caam - limit output IV to CBC to work around CTR mode" failed to apply to 4.14-stable tree

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ed527b13d800dd515a9e6c582f0a73eca65b2e1b Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <[email protected]>
Date: Fri, 31 May 2019 10:13:06 +0200
Subject: [PATCH] crypto: caam - limit output IV to CBC to work around CTR mode
DMA issue

The CAAM driver currently violates an undocumented and slightly controversial requirement imposed by the crypto stack that a buffer referred to by the request structure via its virtual address may not be modified while any scatterlists passed via the same request structure are mapped for inbound DMA.

This may result in errors like

alg: aead: decryption failed on test 1 for gcm_base(ctr-aes-caam,ghash-generic): ret=74
alg: aead: Failed to load transform for gcm(aes): -2

on non-cache coherent systems, due to the fact that the GCM driver passes an IV buffer by virtual address which shares a cacheline with the auth_tag buffer passed via a scatterlist, resulting in corruption of the auth_tag when the IV is updated while the DMA mapping is live.

Since the IV that is returned to the caller is only valid for CBC mode, and given that the in-kernel users of CBC (such as CTS) don't trigger the same issue as the GCM driver, let's just disable the output IV generation for all modes except CBC for the time being.

index 1efa6f5b62cf..4b03c967009b 100644
@@ -977,6 +977,7 @@ static void skcipher_encrypt_done(struct device *jrdev, u32 *desc, u32 err,
 	struct skcipher_request *req = context;
 	struct skcipher_edesc *edesc;
 	struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
+	struct caam_ctx *ctx = crypto_skcipher_ctx(skcipher);
 	int ivsize = crypto_skcipher_ivsize(skcipher);
 
 	dev_dbg(jrdev, "%s %d: err 0x%x\n", __func__, __LINE__, err);

@@ -990,9 +991,9 @@ static void skcipher_encrypt_done(struct device *jrdev, u32 *desc, u32 err,
 
 	/*
 	 * The crypto API expects us to set the IV (req->iv) to the last
-	 * ciphertext block. This is used e.g. by the CTS mode.
+	 * ciphertext block when running in CBC mode.
 	 */
-	if (ivsize)
+	if ((ctx->cdata.algtype & OP_ALG_AAI_MASK) == OP_ALG_AAI_CBC)
 		scatterwalk_map_and_copy(req->iv, req->dst, req->cryptlen -
 					 ivsize, ivsize, 0);
 

@@ -1836,9 +1837,9 @@ static int skcipher_decrypt(struct skcipher_request *req)
 
 	/*
 	 * The crypto API expects us to set the IV (req->iv) to the last
-	 * ciphertext block.
+	 * ciphertext block when running in CBC mode.
 	 */
-	if (ivsize)
+	if ((ctx->cdata.algtype & OP_ALG_AAI_MASK) == OP_ALG_AAI_CBC)
 		scatterwalk_map_and_copy(req->iv, req->src, req->cryptlen -
 					 ivsize, ivsize, 0);