Lucene search

K
redhatcveRedhat.comRH:CVE-2021-47555
HistoryMay 27, 2024 - 9:57 a.m.

CVE-2021-47555

2024-05-2709:57:06
redhat.com
access.redhat.com
1
linux kernel
cve-2021-47555
net: vlan
underflow vulnerability
dev_hold
dev_put
refcnt

6.7 Medium

AI Score

Confidence

Low

0.0004 Low

EPSS

Percentile

15.5%

In the Linux kernel, the following vulnerability has been resolved: net: vlan: fix underflow for the real_dev refcnt Inject error before dev_hold(real_dev) in register_vlan_dev(), and execute the following testcase: ip link add dev dummy1 type dummy ip link add name dummy1.100 link dummy1 type vlan id 100 ip link del dev dummy1 When the dummy netdevice is removed, we will get a WARNING as following: ======================================================================= refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 2 PID: 0 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0 and an endless loop of: ======================================================================= unregister_netdevice: waiting for dummy1 to become free. Usage count = -1073741824 That is because dev_put(real_dev) in vlan_dev_free() be called without dev_hold(real_dev) in register_vlan_dev(). It makes the refcnt of real_dev underflow. Move the dev_hold(real_dev) to vlan_dev_init() which is the call-back of ndo_init(). That makes dev_hold() and dev_put() for vlan’s real_dev symmetrical.

6.7 Medium

AI Score

Confidence

Low

0.0004 Low

EPSS

Percentile

15.5%