From: Vlad Poenaru <vlad.wing@gmail.com> stable inclusion from stable-v6.6.145 commit ec662a8b2cde01e76b37ccd4b992d0342299e69c category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/16648 CVE: CVE-2026-64352 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit 2f884d371fafea137afea504d49ee4a7c8d7985b ] 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 trie's 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. Fixes: 694cea395fde ("bpf: Allow RCU-protected lookups to happen from bh context") Cc: stable@vger.kernel.org Signed-off-by: Vlad Poenaru <vlad.wing@gmail.com> Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Link: https://lore.kernel.org/r/20260609135558.193287-2-vlad.wing@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Tengda Wu <wutengda2@huawei.com> --- kernel/bpf/lpm_trie.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c index 484227a21482..def44994c479 100644 --- a/kernel/bpf/lpm_trie.c +++ b/kernel/bpf/lpm_trie.c @@ -236,7 +236,7 @@ static void *trie_lookup_elem(struct bpf_map *map, void *_key) /* Start walking the trie from the root node ... */ - for (node = rcu_dereference_check(trie->root, rcu_read_lock_bh_held()); + for (node = rcu_dereference_check(trie->root, bpf_rcu_lock_held()); node;) { unsigned int next_bit; size_t matchlen; @@ -270,7 +270,7 @@ static void *trie_lookup_elem(struct bpf_map *map, void *_key) */ next_bit = extract_bit(key->data, node->prefixlen); node = rcu_dereference_check(node->child[next_bit], - rcu_read_lock_bh_held()); + bpf_rcu_lock_held()); } if (!found) -- 2.34.1