CVE-2026-97939

Summary

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

ipmr: account multicast table and route memory

A netadmin in a user+net namespace can create many IPv4 and IPv6 multicast routing tables with MRT_TABLE and MRT6_TABLE. Each unseen id allocates an mr_table via the shared mr_table_alloc(), links it into the per-net list, and leaves it until netns teardown. Those objects were not charged to memcg, so the host unreclaimable slab grows with the table count.

Account mr_table allocations with GFP_KERNEL_ACCOUNT and mark the IPv4/IPv6 MFC caches SLAB_ACCOUNT. This matches the established handling of IP addresses, routes and alternate interface names.

Unresolved MFC entries are still allocated from softIRQ with GFP_ATOMIC and are not charged. They expire after 10 seconds and are bounded by the socket receive queue; see commit 0079ad8e8dc3 ("ipmr: remove hard code cache_resolve_queue_len limit").

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/0264b3ee09b118fec8a5471b4ca288f8ab84722f
• https://git.kernel.org/stable/c/d0a2e2a4ee6bfe51e398bfb6921a7d0f4c26bc1c
• https://git.kernel.org/stable/c/b7ee18725f2292ab554aa96a101ae42d45f008bd

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