CVE-2026-64352

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

bpf: Allow LPM map access from sleepable BPF programs

trie_lookup_elem() annotates its rcu_dereference_check() walks with only rcu_read_lock_bh_held(). Because rcu_dereference_check(p, c) resolves to c || rcu_read_lock_held(), this passes for XDP/NAPI and classic RCU readers but fails for sleepable BPF programs, which enter via __bpf_prog_enter_sleepable() and hold only rcu_read_lock_trace().

trie_update_elem() and trie_delete_elem() have the same problem in a different form: they walk the trie with plain rcu_dereference(), which asserts rcu_read_lock_held() unconditionally. Both are reachable from sleepable BPF programs via the bpf_map_update_elem / bpf_map_delete_elem helpers, and from the syscall path under classic rcu_read_lock(). In the writer paths the trie is actually protected by trie->lock (an rqspinlock taken across the walk); we never relied on the RCU read-side lock to keep nodes alive there.

A sleepable LSM hook that ends up touching an LPM trie therefore triggers lockdep on debug kernels:

============================= WARNING: suspicious RCU usage 7.1.0-… Tainted: G E

kernel/bpf/lpm_trie.c:249 suspicious rcu_dereference_check() usage! 1 lock held by net_tests/540: #0: (rcu_tasks_trace_srcu_struct){….}-{0:0}, at: _bpf_prog_enter_sleepable+0x26/0x280 Call Trace: dump_stack_lvl lockdep_rcu_suspicious trie_lookup_elem bpf_prog…enforce_security_socket_connect bpf_trampoline… security_socket_connect __sys_connect do_syscall_64

This is lockdep-only – no UAF, since Tasks Trace RCU does serialize against the tries reclaim path – but it spams the console once per distinct callsite on every debug kernel running a sleepable BPF LSM that touches an LPM trie, which is increasingly common.

For the lookup path, switch the rcu_dereference_check() annotation from rcu_read_lock_bh_held() to bpf_rcu_lock_held(), which accepts all three contexts (classic, BH, Tasks Trace). Other map types already follow this convention.

For trie_update_elem() and trie_delete_elem(), annotate the walks as rcu_dereference_protected(*p, 1) – matching trie_free() in the same file – since trie->lock is held across the walk. rqspinlock has no lockdep_map, so the predicate degenerates to 1 rather than lockdep_is_held(&trie->lock); the protection is real but not machine-verifiable. trie_get_next_key() also uses bare rcu_dereference() but is reachable only from the BPF syscall, which holds classic rcu_read_lock() before dispatching, so it is left untouched.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/2f884d371fafea137afea504d49ee4a7c8d7985b
• https://git.kernel.org/stable/c/304ca50582f0c047370f85e13caec456f78c9fcc
• https://git.kernel.org/stable/c/57454944737f3ad9a8703aecbbb79713b513a94b
• https://git.kernel.org/stable/c/9bfdf4b81b0e56d47bc6c46c34a46638be716695
• https://git.kernel.org/stable/c/bd6ad9a6b30498d845413e863fb95c6fab3babe3
• https://git.kernel.org/stable/c/ec662a8b2cde01e76b37ccd4b992d0342299e69c
• https://git.kernel.org/stable/c/f0967d4f1ba4323a3cb7dc8fdba74dd3a8caaf04