crypto: arm64/gcm-aes-ce - fix no-NEON fallback code

commit 580e295178402d14bbf598a5702f8e01fc59dbaa upstream.

The arm64 gcm-aes-ce algorithm is failing the extra crypto self-tests
following my patches to test the !may_use_simd() code paths, which
previously were untested.  The problem is that in the !may_use_simd()
case, an odd number of AES blocks can be processed within each step of
the skcipher_walk.  However, the skcipher_walk is being done with a
"stride" of 2 blocks and is advanced by an even number of blocks after
each step.  This causes the encryption to produce the wrong ciphertext
and authentication tag, and causes the decryption to incorrectly fail.

Fix it by only processing an even number of blocks per step.

Fixes: c2b24c36e0a3 ("crypto: arm64/aes-gcm-ce - fix scatterwalk API violation")
Fixes: 71e52c278c54 ("crypto: arm64/aes-ce-gcm - operate on two input blocks at a time")
Cc: <stable@vger.kernel.org> # v4.19+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/crypto/ghash-ce-glue.c b/arch/arm64/crypto/ghash-ce-glue.c
index 067d8937d5af1e74a69ae7b14b1b0306a53fe087..1ed227bf61066c2b7c9b487ced6ab6497508fe51 100644 (file)
--- a/arch/arm64/crypto/ghash-ce-glue.c
+++ b/arch/arm64/crypto/ghash-ce-glue.c
@@ -418,9 +418,11 @@ static int gcm_encrypt(struct aead_request *req)
                put_unaligned_be32(2, iv + GCM_IV_SIZE);
 
                while (walk.nbytes >= (2 * AES_BLOCK_SIZE)) {
-                       int blocks = walk.nbytes / AES_BLOCK_SIZE;
+                       const int blocks =
+                               walk.nbytes / (2 * AES_BLOCK_SIZE) * 2;
                        u8 *dst = walk.dst.virt.addr;
                        u8 *src = walk.src.virt.addr;
+                       int remaining = blocks;
 
                        do {
                                __aes_arm64_encrypt(ctx->aes_key.key_enc,
@@ -430,9 +432,9 @@ static int gcm_encrypt(struct aead_request *req)
 
                                dst += AES_BLOCK_SIZE;
                                src += AES_BLOCK_SIZE;
-                       } while (--blocks > 0);
+                       } while (--remaining > 0);
 
-                       ghash_do_update(walk.nbytes / AES_BLOCK_SIZE, dg,
+                       ghash_do_update(blocks, dg,
                                        walk.dst.virt.addr, &ctx->ghash_key,
                                        NULL);
 
@@ -553,7 +555,7 @@ static int gcm_decrypt(struct aead_request *req)
                put_unaligned_be32(2, iv + GCM_IV_SIZE);
 
                while (walk.nbytes >= (2 * AES_BLOCK_SIZE)) {
-                       int blocks = walk.nbytes / AES_BLOCK_SIZE;
+                       int blocks = walk.nbytes / (2 * AES_BLOCK_SIZE) * 2;
                        u8 *dst = walk.dst.virt.addr;
                        u8 *src = walk.src.virt.addr;