target/linux/generic/backport-5.4/080-wireguard-0071-crypto-arm-chacha-neon-add-missing-counter-increment.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Sun, 13 Dec 2020 15:39:29 +0100
Subject: [PATCH] crypto: arm/chacha-neon - add missing counter increment

commit fd16931a2f518a32753920ff20895e5cf04c8ff1 upstream.

Commit 86cd97ec4b943af3 ("crypto: arm/chacha-neon - optimize for non-block
size multiples") refactored the chacha block handling in the glue code in
a way that may result in the counter increment to be omitted when calling
chacha_block_xor_neon() to process a full block. This violates the skcipher
API, which requires that the output IV is suitable for handling more input
as long as the preceding input has been presented in round multiples of the
block size. Also, the same code is exposed via the chacha library interface
whose callers may actually rely on this increment to occur even for final
blocks that are smaller than the chacha block size.

So increment the counter after calling chacha_block_xor_neon().

Fixes: 86cd97ec4b943af3 ("crypto: arm/chacha-neon - optimize for non-block size multiples")
Reported-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 arch/arm/crypto/chacha-glue.c | 1 +
 1 file changed, 1 insertion(+)

--- a/arch/arm/crypto/chacha-glue.c
+++ b/arch/arm/crypto/chacha-glue.c
@@ -60,6 +60,7 @@ static void chacha_doneon(u32 *state, u8
 		chacha_block_xor_neon(state, d, s, nrounds);
 		if (d != dst)
 			memcpy(dst, buf, bytes);
+		state[12]++;
 	}
 }