[PATCH] ecryptfs: use struct_size() to prevent in integer overflow

[Dan Carpenter]

On 32bit systems the "(sizeof(*msg) + msg->data_len" addition can lead
to integer wrapping.  Use struct_size() for safety.

Fixes: 8bf2debd5f7b ("eCryptfs: introduce device handle for userspace daemon communications")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
---
 fs/ecryptfs/miscdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ecryptfs/miscdev.c b/fs/ecryptfs/miscdev.c
index 4e62c3cef70f..88882f96e06f 100644
--- a/fs/ecryptfs/miscdev.c
+++ b/fs/ecryptfs/miscdev.c
@@ -325,7 +325,7 @@ static int ecryptfs_miscdev_response(struct ecryptfs_daemon *daemon, char *data,
 	struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
 	int rc;
 
-	if ((sizeof(*msg) + msg->data_len) != data_size) {
+	if (struct_size(msg, data, msg->data_len) != data_size) {
 		printk(KERN_WARNING "%s: (sizeof(*msg) + msg->data_len) = "
 		       "[%zd]; data_size = [%zd]. Invalid packet.\n", __func__,
 		       (sizeof(*msg) + msg->data_len), data_size);
-- 
2.45.2