Patch "crypto: ccp - return an actual key size from RSA max_size callback" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

crypto: ccp - return an actual key size from RSA max_size callback

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
crypto-ccp-return-an-actual-key-size-from-rsa-max_size-callback.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Maciej S. Szmigiero" <[email protected]>
Date: Sat, 24 Feb 2018 17:03:21 +0100
Subject: crypto: ccp - return an actual key size from RSA max_size callback

From: Maciej S. Szmigiero <[email protected]>

commit 0a9eb80e643064266868bd2fb2cd608e669309b0 upstream.

rsa-pkcs1pad uses a value returned from a RSA implementation max_size callback as a size of an input buffer passed to the RSA implementation for encrypt and sign operations.

CCP RSA implementation uses a hardware input buffer which size depends only on the current RSA key length, so it should return this key length in the max_size callback, too.
This also matches what the kernel software RSA implementation does.

Previously, the value returned from this callback was always the maximum RSA key size the CCP hardware supports.
This resulted in this huge buffer being passed by rsa-pkcs1pad to CCP even for smaller key sizes and then in a buffer overflow when ccp_run_rsa_cmd() tried to copy this large input buffer into a RSA key length-sized hardware input buffer.

---
 drivers/crypto/ccp/ccp-crypto-rsa.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

@@ -60,10 +60,9 @@ static int ccp_rsa_complete(struct crypt
 
 static unsigned int ccp_rsa_maxsize(struct crypto_akcipher *tfm)
 {
-	if (ccp_version() > CCP_VERSION(3, 0))
-		return CCP5_RSA_MAXMOD;
-	else
-		return CCP_RSA_MAXMOD;
+	struct ccp_ctx *ctx = akcipher_tfm_ctx(tfm);
+
+	return ctx->u.rsa.n_len;
 }
 
 static int ccp_rsa_crypt(struct akcipher_request *req, bool encrypt)

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/crypto-ccp-return-an-actual-key-size-from-rsa-max_size-callback.patch