linux-kernel - [PATCH 4.9 088/199] crypto: ecdh - fix big endian bug in ECC library

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Message-Id: <20191219183219.809163370@linuxfoundation.org>
Date:   Thu, 19 Dec 2019 19:32:50 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 4.9 088/199] crypto: ecdh - fix big endian bug in ECC library

From: Ard Biesheuvel <ard.biesheuvel@...aro.org>

commit f398243e9fd6a3a059c1ea7b380c40628dbf0c61 upstream.

The elliptic curve arithmetic library used by the EC-DH KPP implementation
assumes big endian byte order, and unconditionally reverses the byte
and word order of multi-limb quantities. On big endian systems, the byte
reordering is not necessary, while the word ordering needs to be retained.

So replace the __swab64() invocation with a call to be64_to_cpu() which
should do the right thing for both little and big endian builds.

Fixes: 3c4b23901a0c ("crypto: ecdh - Add ECDH software support")
Cc: <stable@...r.kernel.org> # v4.9+
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 crypto/ecc.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/crypto/ecc.c
+++ b/crypto/ecc.c
@@ -897,10 +897,11 @@ static void ecc_point_mult(struct ecc_po
 static inline void ecc_swap_digits(const u64 *in, u64 *out,
 				   unsigned int ndigits)
 {
+	const __be64 *src = (__force __be64 *)in;
 	int i;
 
 	for (i = 0; i < ndigits; i++)
-		out[i] = __swab64(in[ndigits - 1 - i]);
+		out[i] = be64_to_cpu(src[ndigits - 1 - i]);
 }
 
 int ecc_is_key_valid(unsigned int curve_id, unsigned int ndigits,