arm64 regression fix

- Fix potential clobbering of user vector register state by AES ghash code
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Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 regression fix from Will Deacon:
 "Ard found a nasty arm64 regression in 4.18 where the AES ghash/gcm
  code doesn't notify the kernel about its use of the vector registers,
  therefore potentially corrupting live user state.

  The fix is straightforward and Herbert agreed for it to go via arm64"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  crypto/arm64: aes-ce-gcm - add missing kernel_neon_begin/end pair

arch/arm64/crypto/ghash-ce-glue.c

@@ -488,9 +488,13 @@ static int gcm_decrypt(struct aead_request *req)
 			err = skcipher_walk_done(&walk,
 						 walk.nbytes % AES_BLOCK_SIZE);
 		}
-		if (walk.nbytes)
-			pmull_gcm_encrypt_block(iv, iv, NULL,
+		if (walk.nbytes) {
+			kernel_neon_begin();
+			pmull_gcm_encrypt_block(iv, iv, ctx->aes_key.key_enc,
 						num_rounds(&ctx->aes_key));
+			kernel_neon_end();
+		}
+
 	} else {
 		__aes_arm64_encrypt(ctx->aes_key.key_enc, tag, iv,
 				    num_rounds(&ctx->aes_key));