[PATCH 2/2] xen/xenbus: fix overflow check in xenbus_file_write()

[Konrad Rzeszutek Wilk]

From: Jan Beulich <JBeulich@xxxxxxxx>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
[v1: Rebased on upstream]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 drivers/xen/xenbus/xenbus_dev_frontend.c |    2 +-
 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 89f7625..ac72702 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;
-- 
1.7.7.6

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