NULL Pointer Dereference Affecting kernel-tools-libs package, versions *


Severity

Recommended
0.0
medium
0
10

Based on CentOS security rating.

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  • Snyk IDSNYK-CENTOS9-KERNELTOOLSLIBS-9448516
  • published15 Mar 2025
  • disclosed12 Mar 2025

Introduced: 12 Mar 2025

NewCVE-2025-21864  (opens in a new tab)
CWE-476  (opens in a new tab)

How to fix?

There is no fixed version for Centos:9 kernel-tools-libs.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-tools-libs package and not the kernel-tools-libs package as distributed by Centos. See How to fix? for Centos:9 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

tcp: drop secpath at the same time as we currently drop dst

Xiumei reported hitting the WARN in xfrm6_tunnel_net_exit while running tests that boil down to:

  • create a pair of netns
  • run a basic TCP test over ipcomp6
  • delete the pair of netns

The xfrm_state found on spi_byaddr was not deleted at the time we delete the netns, because we still have a reference on it. This lingering reference comes from a secpath (which holds a ref on the xfrm_state), which is still attached to an skb. This skb is not leaked, it ends up on sk_receive_queue and then gets defer-free'd by skb_attempt_defer_free.

The problem happens when we defer freeing an skb (push it on one CPU's defer_list), and don't flush that list before the netns is deleted. In that case, we still have a reference on the xfrm_state that we don't expect at this point.

We already drop the skb's dst in the TCP receive path when it's no longer needed, so let's also drop the secpath. At this point, tcp_filter has already called into the LSM hooks that may require the secpath, so it should not be needed anymore. However, in some of those places, the MPTCP extension has just been attached to the skb, so we cannot simply drop all extensions.

CVSS Base Scores

version 3.1