From 6fceea0fa59f6786a2847a4cae409117624e8b58 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Mon, 5 Feb 2024 05:56:45 +0000 Subject: bpf: Transfer RCU lock state between subprog calls Allow transferring an imbalanced RCU lock state between subprog calls during verification. This allows patterns where a subprog call returns with an RCU lock held, or a subprog call releases an RCU lock held by the caller. Currently, the verifier would end up complaining if the RCU lock is not released when processing an exit from a subprog, which is non-ideal if its execution is supposed to be enclosed in an RCU read section of the caller. Instead, simply only check whether we are processing exit for frame#0 and do not complain on an active RCU lock otherwise. We only need to update the check when processing BPF_EXIT insn, as copy_verifier_state is already set up to do the right thing. Suggested-by: David Vernet Tested-by: Yafang Shao Acked-by: Yonghong Song Signed-off-by: Kumar Kartikeya Dwivedi Acked-by: David Vernet Link: https://lore.kernel.org/r/20240205055646.1112186-2-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- kernel/bpf/verifier.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'kernel/bpf/verifier.c') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7d38b2343ad4..ddaf09db1175 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -17703,8 +17703,7 @@ process_bpf_exit_full: return -EINVAL; } - if (env->cur_state->active_rcu_lock && - !in_rbtree_lock_required_cb(env)) { + if (env->cur_state->active_rcu_lock && !env->cur_state->curframe) { verbose(env, "bpf_rcu_read_unlock is missing\n"); return -EINVAL; } -- cgit