[PATCH 4.19 233/243] crypto: ecdh - fix big endian bug in ECC library

From: Greg Kroah-Hartman
Date: Wed Dec 11 2019 - 10:26:39 EST

From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>

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@xxxxxxxxxxxxxxx> # v4.9+
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/crypto/ecc.c
+++ b/crypto/ecc.c
@@ -906,10 +906,11 @@ 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]);

static int __ecc_is_key_valid(const struct ecc_curve *curve,