xen/xenbus: fix overflow check in xenbus_file_write()

Acked-by: Ian Campbell <ian.campbell@citrix.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
[v1: Rebased on upstream]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/xen/xenbus/xenbus_dev_frontend.c b/drivers/xen/xenbus/xenbus_dev_frontend.c
index 89f76252a16f..ac727028e658 100644
--- a/drivers/xen/xenbus/xenbus_dev_frontend.c
+++ b/drivers/xen/xenbus/xenbus_dev_frontend.c
@@ -458,7 +458,7 @@ static ssize_t xenbus_file_write(struct file *filp,
                 goto out;
 
         /* Can't write a xenbus message larger we can buffer */
-        if ((len + u->len) > sizeof(u->u.buffer)) {
+        if (len > sizeof(u->u.buffer) - u->len) {
                 /* On error, dump existing buffer */
                 u->len = 0;
                 rc = -EINVAL;