bpf: Preserve inner map identity in callback frames

Summary

In the Linux kernel, the following vulnerability has been resolved: bpf: Preserve inner map identity in callback frames Callback frame constructors initialize map-typed argument registers with __mark_reg_known_zero() and then restore map_ptr. This clears map_uid, which is the only field distinguishing inner maps that share an inner_map_meta template. When a timer callback invokes bpf_for_each_map_elem() on a second inner map, both the saved first map and the second map value can reach the nested callback as the same template with map_uid zero. bpf_timer_init() then accepts pairing the timer from the second map with the first map. The runtime records the first map in the timer without taking a reference. Freeing that map does not find the timer stored in the second map, so a later timer callback dereferences the freed map. Copy map_uid from the same caller register as map_ptr when constructing for-each, timer/workqueue, and task-work callback arguments. The existing identity check can then reject mismatched inner maps while allowing a callback value to be paired with its actual map.

Timeline

1. Sep 25, 2026, 10:23 AM UTCCVE published
2. Oct 21, 2026, 12:54 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 69c087ba6225b574afb6e505b72cb75242a3d844 · fixed in cf85e4f94d7feef8b3c4c90dbe2468595a48393b; From 69c087ba6225b574afb6e505b72cb75242a3d844 · fixed in 166221c52d3ca332f8699a854efca8e2704bb137; From 69c087ba6225b574afb6e505b72cb75242a3d844 · fixed in 08b534bafdd9de65b6374474a8fe719c90eb3b01; From 69c087ba6225b574afb6e505b72cb75242a3d844 · fixed in 66ff2eff093d2a0838f39c713eeb590bc0946c2a; From 69c087ba6225b574afb6e505b72cb75242a3d844 · fixed in b90c5d770dad910fb89e6c1b15052a8a1e8db752

• Linux Linux

  5.13

• KernelLinux

  From 5.13.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.114; From 6.13.0 · fixed in 6.18.57; From 6.19.0 · fixed in 7.2.7

References 5