xenbus_dev: add missing error check to watch handling

So far only the watch path was checked to be zero terminated, while
the watch token was merely assumed to be.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/xen/xenbus/xenbus_dev_frontend.c b/drivers/xen/xenbus/xenbus_dev_frontend.c
index 527dc2a3b89f..89f76252a16f 100644
--- a/drivers/xen/xenbus/xenbus_dev_frontend.c
+++ b/drivers/xen/xenbus/xenbus_dev_frontend.c
@@ -369,6 +369,10 @@ static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
                 goto out;
         }
         token++;
+        if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) {
+                rc = -EILSEQ;
+                goto out;
+        }
 
         if (msg_type == XS_WATCH) {
                 watch = alloc_watch_adapter(path, token);