Linux Kernel up to 5.4.162/5.10.82/5.15.5 register_vlan_dev reference count

Summaryinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 5.4.162/5.10.82/5.15.5. Affected by this issue is the function register_vlan_dev. Executing a manipulation can lead to reference count. This vulnerability is tracked as CVE-2021-47555. No exploit exists. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Linux Kernel up to 5.4.162/5.10.82/5.15.5. This vulnerability affects the function register_vlan_dev. The manipulation with an unknown input leads to a reference count vulnerability. The CWE definition for the vulnerability is CWE-911. The product uses a reference count to manage a resource, but it does not update or incorrectly updates the reference count. As an impact it is known to affect availability. CVE summarizes:

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.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2021-47555 since 05/24/2024. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 246396 (Linux Distros Unpatched Vulnerability : CVE-2021-47555), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.4.163, 5.10.83 or 5.15.6 eliminates this vulnerability. Applying the patch 5e44178864b3/6e800ee43218/f7fc72a508cf/01d9cc2dea3f is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (246396). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.4.162
• 5.10.0
• 5.10.1
• 5.10.2
• 5.10.3
• 5.10.4
• 5.10.5
• 5.10.6
• 5.10.7
• 5.10.8
• 5.10.9
• 5.10.10
• 5.10.11
• 5.10.12
• 5.10.13
• 5.10.14
• 5.10.15
• 5.10.16
• 5.10.17
• 5.10.18
• 5.10.19
• 5.10.20
• 5.10.21
• 5.10.22
• 5.10.23
• 5.10.24
• 5.10.25
• 5.10.26
• 5.10.27
• 5.10.28
• 5.10.29
• 5.10.30
• 5.10.31
• 5.10.32
• 5.10.33
• 5.10.34
• 5.10.35
• 5.10.36
• 5.10.37
• 5.10.38
• 5.10.39
• 5.10.40
• 5.10.41
• 5.10.42
• 5.10.43
• 5.10.44
• 5.10.45
• 5.10.46
• 5.10.47
• 5.10.48
• 5.10.49
• 5.10.50
• 5.10.51
• 5.10.52
• 5.10.53
• 5.10.54
• 5.10.55
• 5.10.56
• 5.10.57
• 5.10.58
• 5.10.59
• 5.10.60
• 5.10.61
• 5.10.62
• 5.10.63
• 5.10.64
• 5.10.65
• 5.10.66
• 5.10.67
• 5.10.68
• 5.10.69
• 5.10.70
• 5.10.71
• 5.10.72
• 5.10.73
• 5.10.74
• 5.10.75
• 5.10.76
• 5.10.77
• 5.10.78
• 5.10.79
• 5.10.80
• 5.10.81
• 5.10.82
• 5.15.0
• 5.15.1
• 5.15.2
• 5.15.3
• 5.15.4
• 5.15.5

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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Entryinfo

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