kernel-5.10: backport chacha non block size optimizations

These make a big difference when doing WireGuard with small armv7
routers, and the 5.4 backport already has it.

Suggested-by: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>
Cc: David Bauer <mail@david-bauer.net>
Cc: Petr Štetiar <ynezz@true.cz>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.10/072-crypto-arm-chacha-neon-add-missing-counter-increment.patch b/target/linux/generic/backport-5.10/072-crypto-arm-chacha-neon-add-missing-counter-increment.patch
new file mode 100644
index 0000000000..1e4d2041e5
--- /dev/null
+++ b/target/linux/generic/backport-5.10/072-crypto-arm-chacha-neon-add-missing-counter-increment.patch
@@ -0,0 +1,38 @@
+From 7f63462faf9eab69132bea9abd48c2c05a93145b Mon Sep 17 00:00:00 2001
+From: Ard Biesheuvel <ardb@kernel.org>
+Date: Sun, 13 Dec 2020 15:39:29 +0100
+Subject: [PATCH 2/2] 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]++;
+ 	}
+ }
+