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, 264 insertions, 0 deletions

diff --git a/arch/mips/mm/sc-mips.c b/arch/mips/mm/sc-mips.c
new file mode 100644
index 000000000..06ec304ad
--- /dev/null
+++ b/arch/mips/mm/sc-mips.c
@@ -0,0 +1,264 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2006 Chris Dearman (chris@mips.com),
+ */
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+
+#include <asm/cpu-type.h>
+#include <asm/mipsregs.h>
+#include <asm/bcache.h>
+#include <asm/cacheops.h>
+#include <asm/page.h>
+#include <asm/mmu_context.h>
+#include <asm/r4kcache.h>
+#include <asm/mips-cps.h>
+#include <asm/bootinfo.h>
+
+/*
+ * MIPS32/MIPS64 L2 cache handling
+ */
+
+/*
+ * Writeback and invalidate the secondary cache before DMA.
+ */
+static void mips_sc_wback_inv(unsigned long addr, unsigned long size)
+{
+	blast_scache_range(addr, addr + size);
+}
+
+/*
+ * Invalidate the secondary cache before DMA.
+ */
+static void mips_sc_inv(unsigned long addr, unsigned long size)
+{
+	unsigned long lsize = cpu_scache_line_size();
+	unsigned long almask = ~(lsize - 1);
+
+	cache_op(Hit_Writeback_Inv_SD, addr & almask);
+	cache_op(Hit_Writeback_Inv_SD, (addr + size - 1) & almask);
+	blast_inv_scache_range(addr, addr + size);
+}
+
+static void mips_sc_enable(void)
+{
+	/* L2 cache is permanently enabled */
+}
+
+static void mips_sc_disable(void)
+{
+	/* L2 cache is permanently enabled */
+}
+
+static void mips_sc_prefetch_enable(void)
+{
+	unsigned long pftctl;
+
+	if (mips_cm_revision() < CM_REV_CM2_5)
+		return;
+
+	/*
+	 * If there is one or more L2 prefetch unit present then enable
+	 * prefetching for both code & data, for all ports.
+	 */
+	pftctl = read_gcr_l2_pft_control();
+	if (pftctl & CM_GCR_L2_PFT_CONTROL_NPFT) {
+		pftctl &= ~CM_GCR_L2_PFT_CONTROL_PAGEMASK;
+		pftctl |= PAGE_MASK & CM_GCR_L2_PFT_CONTROL_PAGEMASK;
+		pftctl |= CM_GCR_L2_PFT_CONTROL_PFTEN;
+		write_gcr_l2_pft_control(pftctl);
+
+		set_gcr_l2_pft_control_b(CM_GCR_L2_PFT_CONTROL_B_PORTID |
+					 CM_GCR_L2_PFT_CONTROL_B_CEN);
+	}
+}
+
+static void mips_sc_prefetch_disable(void)
+{
+	if (mips_cm_revision() < CM_REV_CM2_5)
+		return;
+
+	clear_gcr_l2_pft_control(CM_GCR_L2_PFT_CONTROL_PFTEN);
+	clear_gcr_l2_pft_control_b(CM_GCR_L2_PFT_CONTROL_B_PORTID |
+				   CM_GCR_L2_PFT_CONTROL_B_CEN);
+}
+
+static bool mips_sc_prefetch_is_enabled(void)
+{
+	unsigned long pftctl;
+
+	if (mips_cm_revision() < CM_REV_CM2_5)
+		return false;
+
+	pftctl = read_gcr_l2_pft_control();
+	if (!(pftctl & CM_GCR_L2_PFT_CONTROL_NPFT))
+		return false;
+	return !!(pftctl & CM_GCR_L2_PFT_CONTROL_PFTEN);
+}
+
+static struct bcache_ops mips_sc_ops = {
+	.bc_enable = mips_sc_enable,
+	.bc_disable = mips_sc_disable,
+	.bc_wback_inv = mips_sc_wback_inv,
+	.bc_inv = mips_sc_inv,
+	.bc_prefetch_enable = mips_sc_prefetch_enable,
+	.bc_prefetch_disable = mips_sc_prefetch_disable,
+	.bc_prefetch_is_enabled = mips_sc_prefetch_is_enabled,
+};
+
+/*
+ * Check if the L2 cache controller is activated on a particular platform.
+ * MTI's L2 controller and the L2 cache controller of Broadcom's BMIPS
+ * cores both use c0_config2's bit 12 as "L2 Bypass" bit, that is the
+ * cache being disabled.  However there is no guarantee for this to be
+ * true on all platforms.  In an act of stupidity the spec defined bits
+ * 12..15 as implementation defined so below function will eventually have
+ * to be replaced by a platform specific probe.
+ */
+static inline int mips_sc_is_activated(struct cpuinfo_mips *c)
+{
+	unsigned int config2 = read_c0_config2();
+	unsigned int tmp;
+
+	/* Check the bypass bit (L2B) */
+	switch (current_cpu_type()) {
+	case CPU_34K:
+	case CPU_74K:
+	case CPU_1004K:
+	case CPU_1074K:
+	case CPU_INTERAPTIV:
+	case CPU_PROAPTIV:
+	case CPU_P5600:
+	case CPU_BMIPS5000:
+	case CPU_QEMU_GENERIC:
+	case CPU_P6600:
+		if (config2 & (1 << 12))
+			return 0;
+	}
+
+	tmp = (config2 >> 4) & 0x0f;
+	if (0 < tmp && tmp <= 7)
+		c->scache.linesz = 2 << tmp;
+	else
+		return 0;
+	return 1;
+}
+
+static int mips_sc_probe_cm3(void)
+{
+	struct cpuinfo_mips *c = &current_cpu_data;
+	unsigned long cfg = read_gcr_l2_config();
+	unsigned long sets, line_sz, assoc;
+
+	if (cfg & CM_GCR_L2_CONFIG_BYPASS)
+		return 0;
+
+	sets = cfg & CM_GCR_L2_CONFIG_SET_SIZE;
+	sets >>= __ffs(CM_GCR_L2_CONFIG_SET_SIZE);
+	if (sets)
+		c->scache.sets = 64 << sets;
+
+	line_sz = cfg & CM_GCR_L2_CONFIG_LINE_SIZE;
+	line_sz >>= __ffs(CM_GCR_L2_CONFIG_LINE_SIZE);
+	if (line_sz)
+		c->scache.linesz = 2 << line_sz;
+
+	assoc = cfg & CM_GCR_L2_CONFIG_ASSOC;
+	assoc >>= __ffs(CM_GCR_L2_CONFIG_ASSOC);
+	c->scache.ways = assoc + 1;
+	c->scache.waysize = c->scache.sets * c->scache.linesz;
+	c->scache.waybit = __ffs(c->scache.waysize);
+
+	if (c->scache.linesz) {
+		c->scache.flags &= ~MIPS_CACHE_NOT_PRESENT;
+		c->options |= MIPS_CPU_INCLUSIVE_CACHES;
+		return 1;
+	}
+
+	return 0;
+}
+
+static inline int mips_sc_probe(void)
+{
+	struct cpuinfo_mips *c = &current_cpu_data;
+	unsigned int config1, config2;
+	unsigned int tmp;
+
+	/* Mark as not present until probe completed */
+	c->scache.flags |= MIPS_CACHE_NOT_PRESENT;
+
+	if (mips_cm_revision() >= CM_REV_CM3)
+		return mips_sc_probe_cm3();
+
+	/* Ignore anything but MIPSxx processors */
+	if (!(c->isa_level & (MIPS_CPU_ISA_M32R1 | MIPS_CPU_ISA_M64R1 |
+			      MIPS_CPU_ISA_M32R2 | MIPS_CPU_ISA_M64R2 |
+			      MIPS_CPU_ISA_M32R5 | MIPS_CPU_ISA_M64R5 |
+			      MIPS_CPU_ISA_M32R6 | MIPS_CPU_ISA_M64R6)))
+		return 0;
+
+	/* Does this MIPS32/MIPS64 CPU have a config2 register? */
+	config1 = read_c0_config1();
+	if (!(config1 & MIPS_CONF_M))
+		return 0;
+
+	config2 = read_c0_config2();
+
+	if (!mips_sc_is_activated(c))
+		return 0;
+
+	tmp = (config2 >> 8) & 0x0f;
+	if (tmp <= 7)
+		c->scache.sets = 64 << tmp;
+	else
+		return 0;
+
+	tmp = (config2 >> 0) & 0x0f;
+	if (tmp <= 7)
+		c->scache.ways = tmp + 1;
+	else
+		return 0;
+
+	if (current_cpu_type() == CPU_XBURST) {
+		switch (mips_machtype) {
+		/*
+		 * According to config2 it would be 5-ways, but that is
+		 * contradicted by all documentation.
+		 */
+		case MACH_INGENIC_JZ4770:
+		case MACH_INGENIC_JZ4775:
+			c->scache.ways = 4;
+			break;
+
+		/*
+		 * According to config2 it would be 5-ways and 512-sets,
+		 * but that is contradicted by all documentation.
+		 */
+		case MACH_INGENIC_X1000:
+		case MACH_INGENIC_X1000E:
+			c->scache.sets = 256;
+			c->scache.ways = 4;
+			break;
+		}
+	}
+
+	c->scache.waysize = c->scache.sets * c->scache.linesz;
+	c->scache.waybit = __ffs(c->scache.waysize);
+
+	c->scache.flags &= ~MIPS_CACHE_NOT_PRESENT;
+
+	return 1;
+}
+
+int mips_sc_init(void)
+{
+	int found = mips_sc_probe();
+	if (found) {
+		mips_sc_enable();
+		mips_sc_prefetch_enable();
+		bcops = &mips_sc_ops;
+	}
+	return found;
+}