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, 100 insertions, 0 deletions

diff --git a/arch/mips/pci/ops-mace.c b/arch/mips/pci/ops-mace.c
new file mode 100644
index 000000000..951d8070f
--- /dev/null
+++ b/arch/mips/pci/ops-mace.c
@@ -0,0 +1,100 @@
+/*
+ * 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.
+ *
+ * Copyright (C) 2000, 2001 Keith M Wesolowski
+ */
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include <linux/types.h>
+#include <asm/ip32/mace.h>
+
+#if 0
+# define DPRINTK(args...) printk(args);
+#else
+# define DPRINTK(args...)
+#endif
+
+/*
+ * O2 has up to 5 PCI devices connected into the MACE bridge.  The device
+ * map looks like this:
+ *
+ * 0  aic7xxx 0
+ * 1  aic7xxx 1
+ * 2  expansion slot
+ * 3  N/C
+ * 4  N/C
+ */
+
+static inline int mkaddr(struct pci_bus *bus, unsigned int devfn,
+	unsigned int reg)
+{
+	return ((bus->number & 0xff) << 16) |
+		((devfn & 0xff) << 8) |
+		(reg & 0xfc);
+}
+
+
+static int
+mace_pci_read_config(struct pci_bus *bus, unsigned int devfn,
+		     int reg, int size, u32 *val)
+{
+	u32 control = mace->pci.control;
+
+	/* disable master aborts interrupts during config read */
+	mace->pci.control = control & ~MACEPCI_CONTROL_MAR_INT;
+	mace->pci.config_addr = mkaddr(bus, devfn, reg);
+	switch (size) {
+	case 1:
+		*val = mace->pci.config_data.b[(reg & 3) ^ 3];
+		break;
+	case 2:
+		*val = mace->pci.config_data.w[((reg >> 1) & 1) ^ 1];
+		break;
+	case 4:
+		*val = mace->pci.config_data.l;
+		break;
+	}
+	/* ack possible master abort */
+	mace->pci.error &= ~MACEPCI_ERROR_MASTER_ABORT;
+	mace->pci.control = control;
+	/*
+	 * someone forgot to set the ultra bit for the onboard
+	 * scsi chips; we fake it here
+	 */
+	if (bus->number == 0 && reg == 0x40 && size == 4 &&
+	    (devfn == (1 << 3) || devfn == (2 << 3)))
+		*val |= 0x1000;
+
+	DPRINTK("read%d: reg=%08x,val=%02x\n", size * 8, reg, *val);
+
+	return PCIBIOS_SUCCESSFUL;
+}
+
+static int
+mace_pci_write_config(struct pci_bus *bus, unsigned int devfn,
+		      int reg, int size, u32 val)
+{
+	mace->pci.config_addr = mkaddr(bus, devfn, reg);
+	switch (size) {
+	case 1:
+		mace->pci.config_data.b[(reg & 3) ^ 3] = val;
+		break;
+	case 2:
+		mace->pci.config_data.w[((reg >> 1) & 1) ^ 1] = val;
+		break;
+	case 4:
+		mace->pci.config_data.l = val;
+		break;
+	}
+
+	DPRINTK("write%d: reg=%08x,val=%02x\n", size * 8, reg, val);
+
+	return PCIBIOS_SUCCESSFUL;
+}
+
+struct pci_ops mace_pci_ops = {
+	.read = mace_pci_read_config,
+	.write = mace_pci_write_config,
+};