Patch "crypto: chacha20 - fix handling of chunked input" has been added to the 4.12-stable tree

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

crypto: chacha20 - fix handling of chunked input

to the 4.12-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-chacha20-fix-handling-of-chunked-input.patch
and it can be found in the queue-4.12 subdirectory.

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

From: Ard Biesheuvel <[email protected]>
Date: Mon, 14 Aug 2017 14:28:14 +0100
Subject: crypto: chacha20 - fix handling of chunked input

From: Ard Biesheuvel <[email protected]>

commit 4de437265eaac18f880d827f8e105b10de9b87a3 upstream.

Commit 9ae433bc79f9 ("crypto: chacha20 - convert generic and x86 versions to skcipher") ported the existing chacha20 code to use the new skcipher API, and introduced a bug along the way. Unfortunately, the tcrypt tests did not catch the error, and it was only found recently by Tobias.

Stefan kindly diagnosed the error, and proposed a fix which is similar to the one below, with the exception that 'walk.stride' is used rather than the hardcoded block size. This does not actually matter in this case, but it's a better example of how to use the skcipher walk API.

---
 crypto/chacha20_generic.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

@@ -91,9 +91,14 @@ int crypto_chacha20_crypt(struct skciphe
 	crypto_chacha20_init(state, ctx, walk.iv);
 
 	while (walk.nbytes > 0) {
+		unsigned int nbytes = walk.nbytes;
+
+		if (nbytes < walk.total)
+			nbytes = round_down(nbytes, walk.stride);
+
 		chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
-				 walk.nbytes);
-		err = skcipher_walk_done(&walk, 0);
+				 nbytes);
+		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
 	}
 
 	return err;

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

queue-4.12/crypto-chacha20-fix-handling-of-chunked-input.patch