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NULL Pointer Dereference The advisory has been revoked - it doesn't affect any version of package kernel-rt-debug-kvm  (opens in a new tab)

Threat Intelligence

Exploit Maturity
Not Defined
EPSS
0.04% (13th percentile)

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  • Snyk IDSNYK-CENTOS9-KERNELRTDEBUGKVM-7122254
  • published27 May 2024
  • disclosed24 May 2024
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Introduced: 24 May 2024

CVE-2021-47515  (opens in a new tab)
CWE-476  (opens in a new tab)

Amendment

The Centos security team deemed this advisory irrelevant for Centos:9.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-debug-kvm package and not the kernel-rt-debug-kvm package as distributed by Centos.

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

seg6: fix the iif in the IPv6 socket control block

When an IPv4 packet is received, the ip_rcv_core(...) sets the receiving interface index into the IPv4 socket control block (v5.16-rc4, net/ipv4/ip_input.c line 510):

IPCB(skb)->iif = skb->skb_iif;

If that IPv4 packet is meant to be encapsulated in an outer IPv6+SRH header, the seg6_do_srh_encap(...) performs the required encapsulation. In this case, the seg6_do_srh_encap function clears the IPv6 socket control block (v5.16-rc4 net/ipv6/seg6_iptunnel.c line 163):

memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));

The memset(...) was introduced in commit ef489749aae5 ("ipv6: sr: clear IP6CB(skb) on SRH ip4ip6 encapsulation") a long time ago (2019-01-29).

Since the IPv6 socket control block and the IPv4 socket control block share the same memory area (skb->cb), the receiving interface index info is lost (IP6CB(skb)->iif is set to zero).

As a side effect, that condition triggers a NULL pointer dereference if commit 0857d6f8c759 ("ipv6: When forwarding count rx stats on the orig netdev") is applied.

To fix that issue, we set the IP6CB(skb)->iif with the index of the receiving interface once again.