1 files changed, 38 insertions, 18 deletions

diff --git a/fs/ecryptfs/miscdev.c b/fs/ecryptfs/miscdev.c
index 940a82e..0dc5a3d 100644
--- a/fs/ecryptfs/miscdev.c
+++ b/fs/ecryptfs/miscdev.c
@@ -409,11 +409,47 @@ ecryptfs_miscdev_write(struct file *file, const char __user *buf,
 	ssize_t sz = 0;
 	char *data;
 	uid_t euid = current_euid();
+	unsigned char packet_size_peek[3];
 	int rc;
 
-	if (count == 0)
+	if (count == 0) {
 		goto out;
+	} else if (count == (1 + 4)) {
+		/* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
+		goto memdup;
+	} else if (count < (1 + 4 + 1)
+		   || count > (1 + 4 + 2 + sizeof(struct ecryptfs_message) + 4
+			       + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)) {
+		printk(KERN_WARNING "%s: Acceptable packet size range is "
+		       "[%d-%lu], but amount of data written is [%zu].",
+		       __func__, (1 + 4 + 1),
+		       (1 + 4 + 2 + sizeof(struct ecryptfs_message) + 4
+			+ ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES), count);
+		return -EINVAL;
+	}
+
+	if (copy_from_user(packet_size_peek, (buf + 1 + 4),
+			   sizeof(packet_size_peek))) {
+		printk(KERN_WARNING "%s: Error while inspecting packet size\n",
+		       __func__);
+		return -EFAULT;
+	}
+
+	rc = ecryptfs_parse_packet_length(packet_size_peek, &packet_size,
+					  &packet_size_length);
+	if (rc) {
+		printk(KERN_WARNING "%s: Error parsing packet length; "
+		       "rc = [%d]\n", __func__, rc);
+		return rc;
+	}
+
+	if ((1 + 4 + packet_size_length + packet_size) != count) {
+		printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__,
+		       packet_size);
+		return -EINVAL;
+	}
 
+memdup:
 	data = memdup_user(buf, count);
 	if (IS_ERR(data)) {
 		printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
@@ -435,23 +471,7 @@ ecryptfs_miscdev_write(struct file *file, const char __user *buf,
 		}
 		memcpy(&counter_nbo, &data[i], 4);
 		seq = be32_to_cpu(counter_nbo);
-		i += 4;
-		rc = ecryptfs_parse_packet_length(&data[i], &packet_size,
-						  &packet_size_length);
-		if (rc) {
-			printk(KERN_WARNING "%s: Error parsing packet length; "
-			       "rc = [%d]\n", __func__, rc);
-			goto out_free;
-		}
-		i += packet_size_length;
-		if ((1 + 4 + packet_size_length + packet_size) != count) {
-			printk(KERN_WARNING "%s: (1 + packet_size_length([%zd])"
-			       " + packet_size([%zd]))([%zd]) != "
-			       "count([%zd]). Invalid packet format.\n",
-			       __func__, packet_size_length, packet_size,
-			       (1 + packet_size_length + packet_size), count);
-			goto out_free;
-		}
+		i += 4 + packet_size_length;
 		rc = ecryptfs_miscdev_response(&data[i], packet_size,
 					       euid, current_user_ns(),
 					       task_pid(current), seq);