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, 95 insertions, 0 deletions

diff --git a/arch/mips/dec/tc.c b/arch/mips/dec/tc.c
new file mode 100644
index 000000000..dba583976
--- /dev/null
+++ b/arch/mips/dec/tc.c
@@ -0,0 +1,95 @@
+/*
+ *	TURBOchannel architecture calls.
+ *
+ *	Copyright (c) Harald Koerfgen, 1998
+ *	Copyright (c) 2001, 2003, 2005, 2006  Maciej W. Rozycki
+ *	Copyright (c) 2005  James Simmons
+ *
+ *	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.
+ */
+#include <linux/compiler.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/tc.h>
+#include <linux/types.h>
+
+#include <asm/addrspace.h>
+#include <asm/bootinfo.h>
+#include <asm/paccess.h>
+
+#include <asm/dec/interrupts.h>
+#include <asm/dec/prom.h>
+#include <asm/dec/system.h>
+
+/*
+ * Protected read byte from TURBOchannel slot space.
+ */
+int tc_preadb(u8 *valp, void __iomem *addr)
+{
+	return get_dbe(*valp, (u8 *)addr);
+}
+
+/*
+ * Get TURBOchannel bus information as specified by the spec, plus
+ * the slot space base address and the number of slots.
+ */
+int __init tc_bus_get_info(struct tc_bus *tbus)
+{
+	if (!dec_tc_bus)
+		return -ENXIO;
+
+	memcpy(&tbus->info, rex_gettcinfo(), sizeof(tbus->info));
+	tbus->slot_base = CPHYSADDR((long)rex_slot_address(0));
+
+	switch (mips_machtype) {
+	case MACH_DS5000_200:
+		tbus->num_tcslots = 7;
+		break;
+	case MACH_DS5000_2X0:
+	case MACH_DS5900:
+		tbus->ext_slot_base = 0x20000000;
+		tbus->ext_slot_size = 0x20000000;
+		fallthrough;
+	case MACH_DS5000_1XX:
+		tbus->num_tcslots = 3;
+		break;
+	case MACH_DS5000_XX:
+		tbus->num_tcslots = 2;
+	default:
+		break;
+	}
+	return 0;
+}
+
+/*
+ * Get the IRQ for the specified slot.
+ */
+void __init tc_device_get_irq(struct tc_dev *tdev)
+{
+	switch (tdev->slot) {
+	case 0:
+		tdev->interrupt = dec_interrupt[DEC_IRQ_TC0];
+		break;
+	case 1:
+		tdev->interrupt = dec_interrupt[DEC_IRQ_TC1];
+		break;
+	case 2:
+		tdev->interrupt = dec_interrupt[DEC_IRQ_TC2];
+		break;
+	/*
+	 * Yuck! DS5000/200 onboard devices
+	 */
+	case 5:
+		tdev->interrupt = dec_interrupt[DEC_IRQ_TC5];
+		break;
+	case 6:
+		tdev->interrupt = dec_interrupt[DEC_IRQ_TC6];
+		break;
+	default:
+		tdev->interrupt = -1;
+		break;
+	}
+}