From: Jan Beulich <JBeulich@suse.com>
Date: Wed, 17 Oct 2012 17:14:09 +0000 (-0400)
Subject: xen/xenbus: fix overflow check in xenbus_file_write()
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=1bcaba51eba549748917f7d6eb41900ff9ee3d5f;p=linux-beck.git

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>
---

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;