selftests/bpf: Test rhtab kptr cancellation semanticsgrafted

Resizable hash-map updates and deletions must not perform full special-field
destruction in their caller context. In particular, a referenced kptr must
remain attached to the allocation until the memory allocator destructor can
release it safely.

Add separate coverage for both affected paths. The update test stores a task
kptr, replaces the ordinary value bytes with BPF_EXIST, and verifies that the
kptr survived. The delete test removes an element and exchanges its kptr
through the still-valid map-value pointer before the allocation is reclaimed.

Both cases observe a NULL kptr when rhtab uses bpf_obj_free_fields(). They
recover and release the reference after rhtab switches to cancellation
semantics.

Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>
[ kkd: Split update and delete coverage and rewrote the commit log ]
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904104203.345917-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 40 insertions, 0 deletions

diff --git a/rust/uapi/lib.rs b/rust/uapi/lib.rs
new file mode 100644
index 000000000..797ead5b5
--- /dev/null
+++ b/rust/uapi/lib.rs
@@ -0,0 +1,40 @@
+// 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::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(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES, 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"));