[PATCH] arm64 sha2-ce finup: correct digest for empty data

[Elena Petrova]

The sha256-ce finup implementation for ARM64 produces wrong digest
for empty input (len=0). Expected: the actual digest, result: initial
value of SHA internal state. The error is in sha256_ce_finup:
for empty data `finalize` will be 1, so the code is relying on
sha2_ce_transform to make the final round. However, in
sha256_base_do_update, the block function will not be called when
len == 0.
Fix it by setting finalize to 0 if data is empty.

Fixes: 03802f6a80b3a ("crypto: arm64/sha2-ce - move SHA-224/256 ARMv8 
implementation to base layer")
Cc: sta...@vger.kernel.org
Signed-off-by: Elena Petrova <lena...@google.com>
---
 arch/arm64/crypto/sha2-ce-glue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/crypto/sha2-ce-glue.c b/arch/arm64/crypto/sha2-ce-glue.c
index a725997e55f2..6a5ade974a35 100644
--- a/arch/arm64/crypto/sha2-ce-glue.c
+++ b/arch/arm64/crypto/sha2-ce-glue.c
@@ -60,7 +60,7 @@ static int sha256_ce_finup(struct shash_desc *desc, const u8 
*data,
                           unsigned int len, u8 *out)
 {
        struct sha256_ce_state *sctx = shash_desc_ctx(desc);
-       bool finalize = !sctx->sst.count && !(len % SHA256_BLOCK_SIZE);
+       bool finalize = !sctx->sst.count && !(len % SHA256_BLOCK_SIZE) && len;
 
        if (!crypto_simd_usable()) {
                if (len)
-- 
2.22.0.rc1.257.g3120a18244-goog