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, 85 insertions, 0 deletions

diff --git a/rust/bindings/lib.rs b/rust/bindings/lib.rs
new file mode 100644
index 000000000..439ab88a5
--- /dev/null
+++ b/rust/bindings/lib.rs
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Bindings.
+//!
+//! Imports the generated bindings by `bindgen`.
+//!
+//! This crate may not be directly used. If you need a kernel C API that is
+//! not ported or wrapped in the `kernel` crate, then do so first instead of
+//! using this crate.
+
+#![no_std]
+#![allow(
+    clippy::all,
+    missing_docs,
+    non_camel_case_types,
+    non_upper_case_globals,
+    non_snake_case,
+    improper_ctypes,
+    unreachable_pub,
+    unsafe_op_in_unsafe_fn
+)]
+#![feature(cfi_encoding)]
+
+#[allow(dead_code)]
+#[allow(clippy::as_underscore)]
+#[allow(clippy::cast_lossless)]
+#[allow(clippy::ptr_as_ptr)]
+#[allow(clippy::ref_as_ptr)]
+#[allow(clippy::undocumented_unsafe_blocks)]
+#[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)
+)]
+mod bindings_raw {
+    use pin_init::{MaybeZeroable, Zeroable};
+
+    // Manual definition for blocklisted types.
+    type __kernel_size_t = usize;
+    type __kernel_ssize_t = isize;
+    type __kernel_ptrdiff_t = isize;
+
+    // `bindgen` doesn't automatically do this, see
+    // <https://github.com/rust-lang/rust-bindgen/issues/3196>
+    //
+    // SAFETY: `__BindgenBitfieldUnit<Storage>` is a newtype around `Storage`.
+    unsafe impl<Storage> Zeroable for __BindgenBitfieldUnit<Storage> where Storage: Zeroable {}
+
+    // Use glob import here to expose all helpers.
+    // Symbols defined within the module will take precedence to the glob import.
+    pub use super::bindings_helper::*;
+    include!(concat!(
+        env!("OBJTREE"),
+        "/rust/bindings/bindings_generated.rs"
+    ));
+}
+
+// When both a directly exposed symbol and a helper exists for the same function,
+// the directly exposed symbol is preferred and the helper becomes dead code, so
+// ignore the warning here.
+#[allow(dead_code)]
+mod bindings_helper {
+    // Import the generated bindings for types.
+    use super::bindings_raw::*;
+    include!(concat!(
+        env!("OBJTREE"),
+        "/rust/bindings/bindings_helpers_generated.rs"
+    ));
+}
+
+pub use bindings_raw::*;
+
+pub const compat_ptr_ioctl: Option<
+    unsafe extern "C" fn(*mut file, ffi::c_uint, ffi::c_ulong) -> ffi::c_long,
+> = {
+    #[cfg(CONFIG_COMPAT)]
+    {
+        Some(bindings_raw::compat_ptr_ioctl)
+    }
+    #[cfg(not(CONFIG_COMPAT))]
+    {
+        None
+    }
+};