bpf: Clear rb node linkage when freeing bpf_rb_root

Summary

In the Linux kernel, the following vulnerability has been resolved: bpf: Clear rb node linkage when freeing bpf_rb_root bpf_rb_root_free() detaches the root by copying the current rb_root_cached and then replacing the live root with RB_ROOT_CACHED. It then walks the copied root and drops each object contained in the tree. This leaves the rb node state intact while dropping the object. If the object is refcounted and survives the drop, its bpf_rb_node_kern still contains an owner pointer to the freed root and stale rb tree linkage. If a later bpf_rb_root allocation reuses the same address, bpf_rbtree_remove() can incorrectly pass the owner check and call rb_erase_cached() on a node whose rb pointers belong to the old tree. Mirror the list draining behavior by marking nodes as busy while the root is being detached, then clear the rb node and release the owner before dropping the containing object. This makes surviving nodes unowned and safe to reject from remove or accept for a later add.

Timeline

1. Aug 15, 2026, 5:58 AM UTCCVE published
2. Oct 16, 2026, 6:54 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 21, 2026, 12:45 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 9c395c1b99bd23f74bc628fa000480c49593d17f · fixed in 628a469d2a73e3844e5ee80aa002e232b0fd6493; From 9c395c1b99bd23f74bc628fa000480c49593d17f · fixed in ff3ab3fb956027ab40aca1fb3298cf20dc290273; From 9c395c1b99bd23f74bc628fa000480c49593d17f · fixed in 2eb39de4962f842d653e96818ae372665cd481fd; From 9c395c1b99bd23f74bc628fa000480c49593d17f · fixed in 574612793bed416f6c05fe7c9b50e9eb0441997e; From 9c395c1b99bd23f74bc628fa000480c49593d17f · fixed in 4a7910ee060d8ce55612f5b3cc267f3a265a3cec; From 6.2.15 · fixed in 6.3

• Linux Linux

  6.3

• KernelLinux

  From 6.3.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.114; From 6.13.0 · fixed in 6.18.40; From 6.19.0 · fixed in 7.1.5

References 5