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>

2 files changed, 59 insertions, 0 deletions

diff --git a/rust/uapi/lib.rs b/rust/uapi/lib.rs
new file mode 100644
index 000000000..003e6d4f7
--- /dev/null
+++ b/rust/uapi/lib.rs
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! UAPI Bindings.
+//!
+//! Contains the bindings generated by `bindgen` for UAPI interfaces.
+//!
+//! This crate may be used directly by drivers that need to interact with
+//! userspace APIs.
+
+#![no_std]
+#![allow(
+    clippy::all,
+    clippy::as_underscore,
+    clippy::cast_lossless,
+    clippy::ptr_as_ptr,
+    clippy::ref_as_ptr,
+    clippy::undocumented_unsafe_blocks,
+    dead_code,
+    missing_docs,
+    non_camel_case_types,
+    non_upper_case_globals,
+    non_snake_case,
+    improper_ctypes,
+    unreachable_pub,
+    unsafe_op_in_unsafe_fn
+)]
+#![cfg_attr(not(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES), allow(unknown_lints))]
+#![allow(unnecessary_transmutes)]
+#![cfg_attr(
+    CONFIG_RUSTC_HAS_SUSPICIOUS_RUNTIME_SYMBOL_DEFINITIONS,
+    allow(suspicious_runtime_symbol_definitions)
+)]
+#![feature(cfi_encoding)]
+
+// Manual definition of blocklisted types.
+type __kernel_size_t = usize;
+type __kernel_ssize_t = isize;
+type __kernel_ptrdiff_t = isize;
+
+use pin_init::MaybeZeroable;
+
+include!(concat!(env!("OBJTREE"), "/rust/uapi/uapi_generated.rs"));
diff --git a/rust/uapi/uapi_helper.h b/rust/uapi/uapi_helper.h
new file mode 100644
index 000000000..489748ef6
--- /dev/null
+++ b/rust/uapi/uapi_helper.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Header that contains the headers for which Rust UAPI bindings
+ * will be automatically generated by `bindgen`.
+ *
+ * Sorted alphabetically.
+ */
+
+#include <uapi/drm/drm.h>
+#include <uapi/drm/nova_drm.h>
+#include <uapi/drm/panthor_drm.h>
+#include <uapi/linux/android/binder.h>
+#include <uapi/linux/android/binder_netlink.h>
+#include <uapi/linux/ioctl.h>
+#include <uapi/linux/mdio.h>
+#include <uapi/linux/mii.h>
+#include <uapi/linux/ethtool.h>