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, 145 insertions, 0 deletions

diff --git a/arch/mips/bcm63xx/cs.c b/arch/mips/bcm63xx/cs.c
new file mode 100644
index 000000000..29205badc
--- /dev/null
+++ b/arch/mips/bcm63xx/cs.c
@@ -0,0 +1,145 @@
+/*
+ * 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) 2008 Maxime Bizon <mbizon@freebox.fr>
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/spinlock.h>
+#include <linux/log2.h>
+#include <bcm63xx_cpu.h>
+#include <bcm63xx_io.h>
+#include <bcm63xx_regs.h>
+#include <bcm63xx_cs.h>
+
+static DEFINE_SPINLOCK(bcm63xx_cs_lock);
+
+/*
+ * check if given chip select exists
+ */
+static int is_valid_cs(unsigned int cs)
+{
+	if (cs > 6)
+		return 0;
+	return 1;
+}
+
+/*
+ * Configure chipselect base address and size (bytes).
+ * Size must be a power of two between 8k and 256M.
+ */
+int bcm63xx_set_cs_base(unsigned int cs, u32 base, unsigned int size)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	/* sanity check on size */
+	if (size != roundup_pow_of_two(size))
+		return -EINVAL;
+
+	if (size < 8 * 1024 || size > 256 * 1024 * 1024)
+		return -EINVAL;
+
+	val = (base & MPI_CSBASE_BASE_MASK);
+	/* 8k => 0 - 256M => 15 */
+	val |= (ilog2(size) - ilog2(8 * 1024)) << MPI_CSBASE_SIZE_SHIFT;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	bcm_mpi_writel(val, MPI_CSBASE_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_base);
+
+/*
+ * configure chipselect timing (ns)
+ */
+int bcm63xx_set_cs_timing(unsigned int cs, unsigned int wait,
+			   unsigned int setup, unsigned int hold)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	val = bcm_mpi_readl(MPI_CSCTL_REG(cs));
+	val &= ~(MPI_CSCTL_WAIT_MASK);
+	val &= ~(MPI_CSCTL_SETUP_MASK);
+	val &= ~(MPI_CSCTL_HOLD_MASK);
+	val |= wait << MPI_CSCTL_WAIT_SHIFT;
+	val |= setup << MPI_CSCTL_SETUP_SHIFT;
+	val |= hold << MPI_CSCTL_HOLD_SHIFT;
+	bcm_mpi_writel(val, MPI_CSCTL_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_timing);
+
+/*
+ * configure other chipselect parameter (data bus size, ...)
+ */
+int bcm63xx_set_cs_param(unsigned int cs, u32 params)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	/* none of this fields apply to pcmcia */
+	if (cs == MPI_CS_PCMCIA_COMMON ||
+	    cs == MPI_CS_PCMCIA_ATTR ||
+	    cs == MPI_CS_PCMCIA_IO)
+		return -EINVAL;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	val = bcm_mpi_readl(MPI_CSCTL_REG(cs));
+	val &= ~(MPI_CSCTL_DATA16_MASK);
+	val &= ~(MPI_CSCTL_SYNCMODE_MASK);
+	val &= ~(MPI_CSCTL_TSIZE_MASK);
+	val &= ~(MPI_CSCTL_ENDIANSWAP_MASK);
+	val |= params;
+	bcm_mpi_writel(val, MPI_CSCTL_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_param);
+
+/*
+ * set cs status (enable/disable)
+ */
+int bcm63xx_set_cs_status(unsigned int cs, int enable)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	val = bcm_mpi_readl(MPI_CSCTL_REG(cs));
+	if (enable)
+		val |= MPI_CSCTL_ENABLE_MASK;
+	else
+		val &= ~MPI_CSCTL_ENABLE_MASK;
+	bcm_mpi_writel(val, MPI_CSCTL_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_status);