macvtap: fix uninitialized access on TUNSETIFF
flags field in ifreq is only 16 bit wide, but
we read it as a 32 bit value.
If userspace doesn't zero-initialize unused fields,
this will lead to failures.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 60f7ee5..80fdb82 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -999,7 +999,7 @@
void __user *argp = (void __user *)arg;
struct ifreq __user *ifr = argp;
unsigned int __user *up = argp;
- unsigned int u;
+ unsigned short u;
int __user *sp = argp;
int s;
int ret;
@@ -1014,7 +1014,7 @@
if ((u & ~MACVTAP_FEATURES) != (IFF_NO_PI | IFF_TAP))
ret = -EINVAL;
else
- q->flags = u;
+ q->flags = (q->flags & ~MACVTAP_FEATURES) | u;
return ret;
@@ -1027,8 +1027,9 @@
}
ret = 0;
+ u = q->flags;
if (copy_to_user(&ifr->ifr_name, vlan->dev->name, IFNAMSIZ) ||
- put_user(q->flags, &ifr->ifr_flags))
+ put_user(u, &ifr->ifr_flags))
ret = -EFAULT;
macvtap_put_vlan(vlan);
rtnl_unlock();