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, 63 insertions, 0 deletions

diff --git a/arch/mips/kvm/stats.c b/arch/mips/kvm/stats.c
new file mode 100644
index 000000000..3e6682018
--- /dev/null
+++ b/arch/mips/kvm/stats.c
@@ -0,0 +1,63 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * KVM/MIPS: COP0 access histogram
+ *
+ * Copyright (C) 2012  MIPS Technologies, Inc.  All rights reserved.
+ * Authors: Sanjay Lal <sanjayl@kymasys.com>
+ */
+
+#include <linux/kvm_host.h>
+
+char *kvm_cop0_str[N_MIPS_COPROC_REGS] = {
+	"Index",
+	"Random",
+	"EntryLo0",
+	"EntryLo1",
+	"Context",
+	"PG Mask",
+	"Wired",
+	"HWREna",
+	"BadVAddr",
+	"Count",
+	"EntryHI",
+	"Compare",
+	"Status",
+	"Cause",
+	"EXC PC",
+	"PRID",
+	"Config",
+	"LLAddr",
+	"Watch Lo",
+	"Watch Hi",
+	"X Context",
+	"Reserved",
+	"Impl Dep",
+	"Debug",
+	"DEPC",
+	"PerfCnt",
+	"ErrCtl",
+	"CacheErr",
+	"TagLo",
+	"TagHi",
+	"ErrorEPC",
+	"DESAVE"
+};
+
+void kvm_mips_dump_stats(struct kvm_vcpu *vcpu)
+{
+#ifdef CONFIG_KVM_MIPS_DEBUG_COP0_COUNTERS
+	int i, j;
+
+	kvm_info("\nKVM VCPU[%d] COP0 Access Profile:\n", vcpu->vcpu_id);
+	for (i = 0; i < N_MIPS_COPROC_REGS; i++) {
+		for (j = 0; j < N_MIPS_COPROC_SEL; j++) {
+			if (vcpu->arch.cop0.stat[i][j])
+				kvm_info("%s[%d]: %lu\n", kvm_cop0_str[i], j,
+					 vcpu->arch.cop0.stat[i][j]);
+		}
+	}
+#endif
+}