CVE-2021-46975 Information

Feb 29, 2024 cve

Description

In the Linux kernel the following vulnerability has been resolved:

netfilter: conntrack: Make global sysctls readonly in non-init netns

These sysctls point to global variables:

NF_SYSCTL_CT_MAX (&nf_conntrack_max)
NF_SYSCTL_CT_EXPECT_MAX (&nf_ct_expect_max)
NF_SYSCTL_CT_BUCKETS (&nf_conntrack_htable_size_user)

Because their data pointers are not updated to point to per-netns structures they must be marked read-only in a non-init_net ns. Otherwise changes in any net namespace are reflected in (leaked into) all other net namespaces. This problem has existed since the introduction of net namespaces.

The current logic marks them read-only only if the net namespace is owned by an unprivileged user (other than init_user_ns).

Commit d0febd81ae77 ( etfilter: conntrack: re-visit sysctls in unprivileged namespaces) xposes all sysctls even if the namespace is unpriviliged.\ Since we need to mark them readonly in any case we can forego the unprivileged user check altogether.

Reference

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