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 --- rust/build_error.rs | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100644 rust/build_error.rs (limited to 'rust/build_error.rs') diff --git a/rust/build_error.rs b/rust/build_error.rs new file mode 100644 index 000000000..fa24eeef9 --- /dev/null +++ b/rust/build_error.rs @@ -0,0 +1,31 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Build-time error. +//! +//! This crate provides a [const function][const-functions] `build_error`, which will panic in +//! compile-time if executed in [const context][const-context], and will cause a build error +//! if not executed at compile time and the optimizer does not optimise away the call. +//! +//! It is used by `build_assert!` in the kernel crate, allowing checking of +//! conditions that could be checked statically, but could not be enforced in +//! Rust yet (e.g. perform some checks in [const functions][const-functions], but those +//! functions could still be called in the runtime). +//! +//! For details on constant evaluation in Rust, please see the [Reference][const-eval]. +//! +//! [const-eval]: https://doc.rust-lang.org/reference/const_eval.html +//! [const-functions]: https://doc.rust-lang.org/reference/const_eval.html#const-functions +//! [const-context]: https://doc.rust-lang.org/reference/const_eval.html#const-context + +#![no_std] + +/// Panics if executed in [const context][const-context], or triggers a build error if not. +/// +/// [const-context]: https://doc.rust-lang.org/reference/const_eval.html#const-context +#[inline(never)] +#[cold] +#[export_name = "rust_build_error"] +#[track_caller] +pub const fn build_error(msg: &'static str) -> ! { + panic!("{}", msg); +} -- cgit v1.3.1