Re: [PATCH] crypto: x86/aes-gcm: Disable FPU around skcipher_walk_done().

[Herbert Xu <herbert@gondor.apana.org.au>]

On Fri, Aug 02, 2024 at 09:49:04AM -0700, Eric Biggers wrote:
>
> This would work too, I think:

Yes, and we can go a bit further like this:

diff --git a/arch/x86/crypto/aesni-intel_glue.c b/arch/x86/crypto/aesni-intel_glue.c
index cd37de5ec404..149bc6beae51 100644
--- a/arch/x86/crypto/aesni-intel_glue.c
+++ b/arch/x86/crypto/aesni-intel_glue.c
@@ -1381,8 +1381,9 @@ gcm_crypt(struct aead_request *req, int flags)
 	gcm_process_assoc(key, ghash_acc, req->src, assoclen, flags);
 
 	/* En/decrypt the data and pass the ciphertext through GHASH. */
-	while ((nbytes = walk.nbytes) != 0) {
-		if (unlikely(nbytes < walk.total)) {
+	nbytes = walk.nbytes;
+	if (nbytes) {
+		while (unlikely(nbytes < walk.total)) {
 			/*
 			 * Non-last segment.  In this case, the assembly
 			 * function requires that the length be a multiple of 16
@@ -1397,21 +1398,24 @@ gcm_crypt(struct aead_request *req, int flags)
 			le_ctr[0] += nbytes / AES_BLOCK_SIZE;
 			kernel_fpu_end();
 			err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
+			if (err)
+				return err;
+			nbytes = walk.nbytes;
 			kernel_fpu_begin();
-		} else {
-			/* Last segment: process all remaining data. */
-			aes_gcm_update(key, le_ctr, ghash_acc,
-				       walk.src.virt.addr, walk.dst.virt.addr,
-				       nbytes, flags);
-			err = skcipher_walk_done(&walk, 0);
-			/*
-			 * The low word of the counter isn't used by the
-			 * finalize, so there's no need to increment it here.
-			 */
 		}
+
+		/* Last segment: process all remaining data. */
+		aes_gcm_update(key, le_ctr, ghash_acc,
+			       walk.src.virt.addr, walk.dst.virt.addr,
+			       nbytes, flags);
+		/*
+		 * The low word of the counter isn't used by the
+		 * finalize, so there's no need to increment it here.
+		 */
+	} else if (err) {
+		kernel_fpu_end();
+		return err;
 	}
-	if (err)
-		goto out;
 
 	/* Finalize */
 	taglen = crypto_aead_authsize(tfm);
@@ -1439,9 +1443,8 @@ gcm_crypt(struct aead_request *req, int flags)
 				       datalen, tag, taglen, flags))
 			err = -EBADMSG;
 	}
-out:
 	kernel_fpu_end();
-	return err;
+	return skcipher_walk_done(&walk, 0);
 }
 
 #define DEFINE_GCM_ALGS(suffix, flags, generic_driver_name, rfc_driver_name,   \
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt