Address review: fix remaining check in nfs4_decode_nfsace4

fs/nfs/nfs4proc.c

@@ -7933,7 +7933,7 @@ static bool numeric_name_to_id(const char *name, u32 namelen, unsigned long long
 static int nfs4_decode_nfsace4(void **data, size_t *remaining, struct nfs4_ace *ace)
 {
 	u32 *p = *data;
-	u32 length;
+	u32 length, length_incl_padding;
 	int error = 0;
 
 	/*
@@ -7963,16 +7963,15 @@ static int nfs4_decode_nfsace4(void **data, size_t *remaining, struct nfs4_ace *
 	ace->flag = ntohl(*(p++));
 	ace->access_mask = ntohl(*(p++));
 	length = ntohl(*(p++));
+	length_incl_padding = XDR_QUADLEN(length) << 2;
 
 	/*
 	 * Now that we have the length, check remaining again.
 	 *
-	 * There could be an argument that we check against:
-	 *     (NFSACE4_HEADER_BYTES + XDR_QUADLEN(length))
-	 * however since we won't actually access any of those trailing
-	 * padding bytes in this call, it doesn't really matter.
+	 * The input buffer includes both the string and null
+	 * padding (if necessary to align things).
 	 */
-	if (*remaining < (NFSACE4_HEADER_BYTES + length)) {
+	if (*remaining < (NFSACE4_HEADER_BYTES + length_incl_padding)) {
 		pr_err("NFS: %s buffer not large enough to contain ACE who", __func__);
 		return -EOVERFLOW;
 	}
@@ -8022,7 +8021,7 @@ static int nfs4_decode_nfsace4(void **data, size_t *remaining, struct nfs4_ace *
 		p += XDR_QUADLEN(length);
 		*data = p;
 		/* Reduce remaining by initial 4 uint32_t + the string (incl padding) */
-		*remaining -= (NFSACE4_HEADER_BYTES + length);
+		*remaining -= (NFSACE4_HEADER_BYTES + length_incl_padding);
 	}
 	return error;
 }