selftests/bpf: Reject graph kptr use after RCU unlockgrafted

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 <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 31 insertions, 0 deletions

diff --git a/rust/proc-macro2/location.rs b/rust/proc-macro2/location.rs
new file mode 100644
index 000000000..3a11871e2
--- /dev/null
+++ b/rust/proc-macro2/location.rs
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use core::cmp::Ordering;
+
+/// A line-column pair representing the start or end of a `Span`.
+///
+/// This type is semver exempt and not exposed by default.
+#[cfg_attr(docsrs, doc(cfg(feature = "span-locations")))]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub struct LineColumn {
+    /// The 1-indexed line in the source file on which the span starts or ends
+    /// (inclusive).
+    pub line: usize,
+    /// The 0-indexed column (in UTF-8 characters) in the source file on which
+    /// the span starts or ends (inclusive).
+    pub column: usize,
+}
+
+impl Ord for LineColumn {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.line
+            .cmp(&other.line)
+            .then(self.column.cmp(&other.column))
+    }
+}
+
+impl PartialOrd for LineColumn {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}