CVE-2024-56638

/// Technical description

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

netfilter: nft_inner: incorrect percpu area handling under softirq

Softirq can interrupt ongoing packet from process context that is

walking over the percpu area that contains inner header offsets.

Disable bh and perform three checks before restoring the percpu inner

header offsets to validate that the percpu area is valid for this

skbuff:

1) If the NFT_PKTINFO_INNER_FULL flag is set on, then this skbuff

has already been parsed before for inner header fetching to

register.

2) Validate that the percpu area refers to this skbuff using the

skbuff pointer as a cookie. If there is a cookie mismatch, then

this skbuff needs to be parsed again.

3) Finally, validate if the percpu area refers to this tunnel type.

Only after these three checks the percpu area is restored to a on-stack

copy and bh is enabled again.

After inner header fetching, the on-stack copy is stored back to the

percpu area.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References