selftests/bpf: Test packet range of pointers sharing an idgrafted

Add tests where two packet pointers share an id and tightening one
pointer's umax from its var_off would put it less than their constant
distance from the other's umax: with an index & 0x38 capped at 50, the
base pointer keeps umax 50, so the pointer 8 bytes further on must keep
umax 58, even though its known bits allow at most 56.

These refused a valid program or accepted an out-of-bounds access before
the fix:

- check the advanced copy, load through the base: valid, was refused;
- check the base, load the byte at base + 1 through a copy advanced by
  8: was accepted;
- check base + 4, load 4 bytes at base + 2 through base + 8: reads two
  bytes past the checked range, was accepted;
- the same as the second with data_meta pointers checked against data:
  was accepted.

These pass with and without the fix and cover nearby paths:

- subtract an unknown scalar from a checked pointer and load below it
  (the range is kept across a new id);
- reach a load through two paths whose checks cover 8 and 7 bytes after
  the loaded pointer; the second path must not be pruned by the first;
- spill a copy of a pointer, check the pointer, fill the copy and load
  one byte past the checked range: the load is refused, and the copy
  has the range of the check.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20261001145255.855630-2-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 121 insertions, 0 deletions

diff --git a/include/kunit/of.h b/include/kunit/of.h
new file mode 100644
index 000000000..75a760a4e
--- /dev/null
+++ b/include/kunit/of.h
@@ -0,0 +1,121 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _KUNIT_OF_H
+#define _KUNIT_OF_H
+
+#include <kunit/test.h>
+
+struct device_node;
+
+#ifdef CONFIG_OF
+
+void of_node_put_kunit(struct kunit *test, struct device_node *node);
+
+#else
+
+static inline
+void of_node_put_kunit(struct kunit *test, struct device_node *node)
+{
+	kunit_skip(test, "requires CONFIG_OF");
+}
+
+#endif /* !CONFIG_OF */
+
+#if defined(CONFIG_OF) && defined(CONFIG_OF_OVERLAY) && defined(CONFIG_OF_EARLY_FLATTREE)
+
+int of_overlay_fdt_apply_kunit(struct kunit *test, void *overlay_fdt,
+			       u32 overlay_fdt_size, int *ovcs_id);
+#else
+
+static inline int
+of_overlay_fdt_apply_kunit(struct kunit *test, void *overlay_fdt,
+			   u32 overlay_fdt_size, int *ovcs_id)
+{
+	kunit_skip(test, "requires CONFIG_OF and CONFIG_OF_OVERLAY and CONFIG_OF_EARLY_FLATTREE for root node");
+	return -EINVAL;
+}
+
+#endif
+
+/**
+ * __of_overlay_apply_kunit() - Test managed of_overlay_fdt_apply() variant
+ * @test: test context
+ * @overlay_begin: start address of overlay to apply
+ * @overlay_end: end address of overlay to apply
+ *
+ * This is mostly internal API. See of_overlay_apply_kunit() for the wrapper
+ * that makes this easier to use.
+ *
+ * Similar to of_overlay_fdt_apply(), except the overlay is managed by the test
+ * case and is automatically removed with of_overlay_remove() after the test
+ * case concludes.
+ *
+ * Return: 0 on success, negative errno on failure
+ */
+static inline int __of_overlay_apply_kunit(struct kunit *test,
+					   u8 *overlay_begin,
+					   const u8 *overlay_end)
+{
+	int unused;
+
+	return of_overlay_fdt_apply_kunit(test, overlay_begin,
+					  overlay_end - overlay_begin,
+					  &unused);
+}
+
+#define of_overlay_begin(overlay_name) __dtbo_##overlay_name##_begin
+#define of_overlay_end(overlay_name) __dtbo_##overlay_name##_end
+
+#define OF_OVERLAY_DECLARE(overlay_name)			\
+	extern uint8_t of_overlay_begin(overlay_name)[];	\
+	extern uint8_t of_overlay_end(overlay_name)[]		\
+
+/**
+ * of_overlay_apply_kunit() - Test managed of_overlay_fdt_apply() for built-in overlays
+ * @test: test context
+ * @overlay_name: name of overlay to apply
+ *
+ * This macro is used to apply a device tree overlay built with the
+ * cmd_dt_S_dtbo rule in scripts/Makefile.lib that has been compiled into the
+ * kernel image or KUnit test module. The overlay is automatically removed when
+ * the test is finished.
+ *
+ * Unit tests that need device tree nodes should compile an overlay file with
+ * @overlay_name\.dtbo.o in their Makefile along with their unit test and then
+ * load the overlay during their test. The @overlay_name matches the filename
+ * of the overlay without the dtbo filename extension. If CONFIG_OF_OVERLAY is
+ * not enabled, the @test will be skipped.
+ *
+ * In the Makefile
+ *
+ * .. code-block:: none
+ *
+ *	obj-$(CONFIG_OF_OVERLAY_KUNIT_TEST) += overlay_test.o kunit_overlay_test.dtbo.o
+ *
+ * In the test
+ *
+ * .. code-block:: c
+ *
+ *	static void of_overlay_kunit_of_overlay_apply(struct kunit *test)
+ *	{
+ *		struct device_node *np;
+ *
+ *		KUNIT_ASSERT_EQ(test, 0,
+ *				of_overlay_apply_kunit(test, kunit_overlay_test));
+ *
+ *		np = of_find_node_by_name(NULL, "test-kunit");
+ *		KUNIT_EXPECT_NOT_ERR_OR_NULL(test, np);
+ *		of_node_put(np);
+ *	}
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+#define of_overlay_apply_kunit(test, overlay_name)		\
+({								\
+	OF_OVERLAY_DECLARE(overlay_name);			\
+								\
+	__of_overlay_apply_kunit((test),			\
+			of_overlay_begin(overlay_name),		\
+			of_overlay_end(overlay_name));		\
+})
+
+#endif