From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- include/net/netns/generic.h | 52 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 include/net/netns/generic.h (limited to 'include/net/netns/generic.h') diff --git a/include/net/netns/generic.h b/include/net/netns/generic.h new file mode 100644 index 000000000..00c399ede --- /dev/null +++ b/include/net/netns/generic.h @@ -0,0 +1,52 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * generic net pointers + */ + +#ifndef __NET_GENERIC_H__ +#define __NET_GENERIC_H__ + +#include +#include +#include + +/* + * Generic net pointers are to be used by modules to put some private + * stuff on the struct net without explicit struct net modification + * + * The rules are simple: + * 1. set pernet_operations->id. After register_pernet_device you + * will have the id of your private pointer. + * 2. set pernet_operations->size to have the code allocate and free + * a private structure pointed to from struct net. + * 3. do not change this pointer while the net is alive; + * 4. do not try to have any private reference on the net_generic object. + * + * After accomplishing all of the above, the private pointer can be + * accessed with the net_generic() call. + */ + +struct net_generic { + union { + struct { + unsigned int len; + struct rcu_head rcu; + } s; + + DECLARE_FLEX_ARRAY(void *, ptr); + }; +}; + +static inline void *net_generic(const struct net *net, unsigned int id) +{ + struct net_generic *ng; + void *ptr; + + rcu_read_lock(); + ng = rcu_dereference(net->gen); + ptr = ng->ptr[id]; + rcu_read_unlock(); + + return ptr; +} +#endif -- cgit v1.3.1