From: Alice Ryhl By default bindgen will convert 'enum lru_status' into a typedef for an integer. For the most part, an integer of the same size as the enum results in the correct ABI, but in the specific case of CFI, that is not the case. The CFI encoding is supposed to be the same as a struct called 'lru_status' rather than the name of the underlying native integer type. To fix this, tell bindgen to generate a newtype and set the CFI type explicitly. Note that we need to set the CFI attribute explicitly as bindgen is using repr(transparent), which is otherwise identical to the inner type for ABI purposes. This allows us to remove the page range helper C function in Binder without risking a CFI failure when list_lru_walk calls the provided function pointer. The --with-attribute-custom-enum argument requires bindgen v0.71 or greater. [ In particular, the feature was added in 0.71.0 [1][2]. In addition, `feature(cfi_encoding)` has been available since Rust 1.71.0 [3]. Link: https://github.com/rust-lang/rust-bindgen/issues/2520 [1] Link: https://github.com/rust-lang/rust-bindgen/pull/2866 [2] Link: https://github.com/rust-lang/rust/pull/105452 [3] - Miguel ] My testing procedure was to add this to the android17-6.18 branch and verify that rust_shrink_free_page is successfully called without crash, and verify that it does in fact crash when the cfi_encoding is set to other values. Note that I couldn't test this on android16-6.12 as that branch uses a bindgen version that is too old. Signed-off-by: Alice Ryhl Link: https://patch.msgid.link/20260223-cfi-lru-status-v2-1-89c6448a63a4@google.com [ Rebased on top of the minimum Rust version bump series which provide the required `bindgen` version. - Miguel ] Signed-off-by: Miguel Ojeda --- drivers/android/binder/Makefile | 3 +-- drivers/android/binder/page_range.rs | 6 +++--- drivers/android/binder/page_range_helper.c | 24 ---------------------- drivers/android/binder/page_range_helper.h | 15 -------------- rust/bindgen_parameters | 4 ++++ rust/bindings/bindings_helper.h | 1 - rust/bindings/lib.rs | 1 + rust/uapi/lib.rs | 1 + 8 files changed, 10 insertions(+), 45 deletions(-) delete mode 100644 drivers/android/binder/page_range_helper.c delete mode 100644 drivers/android/binder/page_range_helper.h diff --git a/drivers/android/binder/Makefile b/drivers/android/binder/Makefile index 09eabb527fa0..7e0cd9782a8b 100644 --- a/drivers/android/binder/Makefile +++ b/drivers/android/binder/Makefile @@ -5,5 +5,4 @@ obj-$(CONFIG_ANDROID_BINDER_IPC_RUST) += rust_binder.o rust_binder-y := \ rust_binder_main.o \ rust_binderfs.o \ - rust_binder_events.o \ - page_range_helper.o + rust_binder_events.o diff --git a/drivers/android/binder/page_range.rs b/drivers/android/binder/page_range.rs index fdd97112ef5c..8e9f5c4819d0 100644 --- a/drivers/android/binder/page_range.rs +++ b/drivers/android/binder/page_range.rs @@ -642,15 +642,15 @@ fn drop(self: Pin<&mut Self>) { unsafe { bindings::list_lru_walk( list_lru, - Some(bindings::rust_shrink_free_page_wrap), + Some(rust_shrink_free_page), ptr::null_mut(), nr_to_scan, ) } } -const LRU_SKIP: bindings::lru_status = bindings::lru_status_LRU_SKIP; -const LRU_REMOVED_ENTRY: bindings::lru_status = bindings::lru_status_LRU_REMOVED_RETRY; +const LRU_SKIP: bindings::lru_status = bindings::lru_status::LRU_SKIP; +const LRU_REMOVED_ENTRY: bindings::lru_status = bindings::lru_status::LRU_REMOVED_RETRY; /// # Safety /// Called by the shrinker. diff --git a/drivers/android/binder/page_range_helper.c b/drivers/android/binder/page_range_helper.c deleted file mode 100644 index 496887723ee0..000000000000 --- a/drivers/android/binder/page_range_helper.c +++ /dev/null @@ -1,24 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0 - -/* C helper for page_range.rs to work around a CFI violation. - * - * Bindgen currently pretends that `enum lru_status` is the same as an integer. - * This assumption is fine ABI-wise, but once you add CFI to the mix, it - * triggers a CFI violation because `enum lru_status` gets a different CFI tag. - * - * This file contains a workaround until bindgen can be fixed. - * - * Copyright (C) 2025 Google LLC. - */ -#include "page_range_helper.h" - -unsigned int rust_shrink_free_page(struct list_head *item, - struct list_lru_one *list, - void *cb_arg); - -enum lru_status -rust_shrink_free_page_wrap(struct list_head *item, struct list_lru_one *list, - void *cb_arg) -{ - return rust_shrink_free_page(item, list, cb_arg); -} diff --git a/drivers/android/binder/page_range_helper.h b/drivers/android/binder/page_range_helper.h deleted file mode 100644 index 18dd2dd117b2..000000000000 --- a/drivers/android/binder/page_range_helper.h +++ /dev/null @@ -1,15 +0,0 @@ -/* SPDX-License-Identifier: GPL-2.0 */ -/* - * Copyright (C) 2025 Google, Inc. - */ - -#ifndef _LINUX_PAGE_RANGE_HELPER_H -#define _LINUX_PAGE_RANGE_HELPER_H - -#include - -enum lru_status -rust_shrink_free_page_wrap(struct list_head *item, struct list_lru_one *list, - void *cb_arg); - -#endif /* _LINUX_PAGE_RANGE_HELPER_H */ diff --git a/rust/bindgen_parameters b/rust/bindgen_parameters index 112ec197ef0a..6f02d9720ad2 100644 --- a/rust/bindgen_parameters +++ b/rust/bindgen_parameters @@ -19,6 +19,10 @@ # warning. We don't need to peek into it anyway. --opaque-type spinlock +# enums that appear in indirect function calls should specify a cfi type +--newtype-enum lru_status +--with-attribute-custom-enum=lru_status='#[cfi_encoding="10lru_status"]' + # `seccomp`'s comment gets understood as a doctest --no-doc-comments diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index 083cc44aa952..faf3ee634ced 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -149,5 +149,4 @@ const vm_flags_t RUST_CONST_HELPER_VM_NOHUGEPAGE = VM_NOHUGEPAGE; #if IS_ENABLED(CONFIG_ANDROID_BINDER_IPC_RUST) #include "../../drivers/android/binder/rust_binder.h" #include "../../drivers/android/binder/rust_binder_events.h" -#include "../../drivers/android/binder/page_range_helper.h" #endif diff --git a/rust/bindings/lib.rs b/rust/bindings/lib.rs index e18c160dad17..854e7c471434 100644 --- a/rust/bindings/lib.rs +++ b/rust/bindings/lib.rs @@ -19,6 +19,7 @@ unreachable_pub, unsafe_op_in_unsafe_fn )] +#![feature(cfi_encoding)] #[allow(dead_code)] #[allow(clippy::cast_lossless)] diff --git a/rust/uapi/lib.rs b/rust/uapi/lib.rs index 821e286e0daa..b8a515de31ca 100644 --- a/rust/uapi/lib.rs +++ b/rust/uapi/lib.rs @@ -24,6 +24,7 @@ unsafe_op_in_unsafe_fn )] #![cfg_attr(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES, allow(unnecessary_transmutes))] +#![feature(cfi_encoding)] // Manual definition of blocklisted types. type __kernel_size_t = usize; -- 2.53.0