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authorBenno Lossin <benno.lossin@proton.me>2024-04-01 18:52:50 +0000
committerMiguel Ojeda <ojeda@kernel.org>2024-04-16 21:13:43 +0200
commit7044dcff8301b29269016ebd17df27c4736140d2 (patch)
tree548e126314b26a51f0145d95359392f1e073683a /rust
parent49ceae68a0df9a92617a61e9ce8a0efcf6419585 (diff)
rust: macros: fix soundness issue in `module!` macro
The `module!` macro creates glue code that are called by C to initialize the Rust modules using the `Module::init` function. Part of this glue code are the local functions `__init` and `__exit` that are used to initialize/destroy the Rust module. These functions are safe and also visible to the Rust mod in which the `module!` macro is invoked. This means that they can be called by other safe Rust code. But since they contain `unsafe` blocks that rely on only being called at the right time, this is a soundness issue. Wrap these generated functions inside of two private modules, this guarantees that the public functions cannot be called from the outside. Make the safe functions `unsafe` and add SAFETY comments. Cc: stable@vger.kernel.org Reported-by: Björn Roy Baron <bjorn3_gh@protonmail.com> Closes: https://github.com/Rust-for-Linux/linux/issues/629 Fixes: 1fbde52bde73 ("rust: add `macros` crate") Signed-off-by: Benno Lossin <benno.lossin@proton.me> Reviewed-by: Wedson Almeida Filho <walmeida@microsoft.com> Link: https://lore.kernel.org/r/20240401185222.12015-1-benno.lossin@proton.me [ Moved `THIS_MODULE` out of the private-in-private modules since it should remain public, as Dirk Behme noticed [1]. Capitalized comments, avoided newline in non-list SAFETY comments and reworded to add Reported-by and newline. ] Link: https://rust-for-linux.zulipchat.com/#narrow/stream/291565-Help/topic/x/near/433512583 [1] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Diffstat (limited to 'rust')
-rw-r--r--rust/macros/module.rs190
1 files changed, 115 insertions, 75 deletions
diff --git a/rust/macros/module.rs b/rust/macros/module.rs
index 27979e582e4b..acd0393b5095 100644
--- a/rust/macros/module.rs
+++ b/rust/macros/module.rs
@@ -199,17 +199,6 @@ pub(crate) fn module(ts: TokenStream) -> TokenStream {
/// Used by the printing macros, e.g. [`info!`].
const __LOG_PREFIX: &[u8] = b\"{name}\\0\";
- /// The \"Rust loadable module\" mark.
- //
- // This may be best done another way later on, e.g. as a new modinfo
- // key or a new section. For the moment, keep it simple.
- #[cfg(MODULE)]
- #[doc(hidden)]
- #[used]
- static __IS_RUST_MODULE: () = ();
-
- static mut __MOD: Option<{type_}> = None;
-
// SAFETY: `__this_module` is constructed by the kernel at load time and will not be
// freed until the module is unloaded.
#[cfg(MODULE)]
@@ -221,81 +210,132 @@ pub(crate) fn module(ts: TokenStream) -> TokenStream {
kernel::ThisModule::from_ptr(core::ptr::null_mut())
}};
- // Loadable modules need to export the `{{init,cleanup}}_module` identifiers.
- /// # Safety
- ///
- /// This function must not be called after module initialization, because it may be
- /// freed after that completes.
- #[cfg(MODULE)]
- #[doc(hidden)]
- #[no_mangle]
- #[link_section = \".init.text\"]
- pub unsafe extern \"C\" fn init_module() -> core::ffi::c_int {{
- __init()
- }}
-
- #[cfg(MODULE)]
- #[doc(hidden)]
- #[no_mangle]
- pub extern \"C\" fn cleanup_module() {{
- __exit()
- }}
+ // Double nested modules, since then nobody can access the public items inside.
+ mod __module_init {{
+ mod __module_init {{
+ use super::super::{type_};
+
+ /// The \"Rust loadable module\" mark.
+ //
+ // This may be best done another way later on, e.g. as a new modinfo
+ // key or a new section. For the moment, keep it simple.
+ #[cfg(MODULE)]
+ #[doc(hidden)]
+ #[used]
+ static __IS_RUST_MODULE: () = ();
+
+ static mut __MOD: Option<{type_}> = None;
+
+ // Loadable modules need to export the `{{init,cleanup}}_module` identifiers.
+ /// # Safety
+ ///
+ /// This function must not be called after module initialization, because it may be
+ /// freed after that completes.
+ #[cfg(MODULE)]
+ #[doc(hidden)]
+ #[no_mangle]
+ #[link_section = \".init.text\"]
+ pub unsafe extern \"C\" fn init_module() -> core::ffi::c_int {{
+ // SAFETY: This function is inaccessible to the outside due to the double
+ // module wrapping it. It is called exactly once by the C side via its
+ // unique name.
+ unsafe {{ __init() }}
+ }}
- // Built-in modules are initialized through an initcall pointer
- // and the identifiers need to be unique.
- #[cfg(not(MODULE))]
- #[cfg(not(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS))]
- #[doc(hidden)]
- #[link_section = \"{initcall_section}\"]
- #[used]
- pub static __{name}_initcall: extern \"C\" fn() -> core::ffi::c_int = __{name}_init;
+ #[cfg(MODULE)]
+ #[doc(hidden)]
+ #[no_mangle]
+ pub extern \"C\" fn cleanup_module() {{
+ // SAFETY:
+ // - This function is inaccessible to the outside due to the double
+ // module wrapping it. It is called exactly once by the C side via its
+ // unique name,
+ // - furthermore it is only called after `init_module` has returned `0`
+ // (which delegates to `__init`).
+ unsafe {{ __exit() }}
+ }}
- #[cfg(not(MODULE))]
- #[cfg(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)]
- core::arch::global_asm!(
- r#\".section \"{initcall_section}\", \"a\"
- __{name}_initcall:
- .long __{name}_init - .
- .previous
- \"#
- );
+ // Built-in modules are initialized through an initcall pointer
+ // and the identifiers need to be unique.
+ #[cfg(not(MODULE))]
+ #[cfg(not(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS))]
+ #[doc(hidden)]
+ #[link_section = \"{initcall_section}\"]
+ #[used]
+ pub static __{name}_initcall: extern \"C\" fn() -> core::ffi::c_int = __{name}_init;
+
+ #[cfg(not(MODULE))]
+ #[cfg(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)]
+ core::arch::global_asm!(
+ r#\".section \"{initcall_section}\", \"a\"
+ __{name}_initcall:
+ .long __{name}_init - .
+ .previous
+ \"#
+ );
+
+ #[cfg(not(MODULE))]
+ #[doc(hidden)]
+ #[no_mangle]
+ pub extern \"C\" fn __{name}_init() -> core::ffi::c_int {{
+ // SAFETY: This function is inaccessible to the outside due to the double
+ // module wrapping it. It is called exactly once by the C side via its
+ // placement above in the initcall section.
+ unsafe {{ __init() }}
+ }}
- #[cfg(not(MODULE))]
- #[doc(hidden)]
- #[no_mangle]
- pub extern \"C\" fn __{name}_init() -> core::ffi::c_int {{
- __init()
- }}
+ #[cfg(not(MODULE))]
+ #[doc(hidden)]
+ #[no_mangle]
+ pub extern \"C\" fn __{name}_exit() {{
+ // SAFETY:
+ // - This function is inaccessible to the outside due to the double
+ // module wrapping it. It is called exactly once by the C side via its
+ // unique name,
+ // - furthermore it is only called after `__{name}_init` has returned `0`
+ // (which delegates to `__init`).
+ unsafe {{ __exit() }}
+ }}
- #[cfg(not(MODULE))]
- #[doc(hidden)]
- #[no_mangle]
- pub extern \"C\" fn __{name}_exit() {{
- __exit()
- }}
+ /// # Safety
+ ///
+ /// This function must only be called once.
+ unsafe fn __init() -> core::ffi::c_int {{
+ match <{type_} as kernel::Module>::init(&super::super::THIS_MODULE) {{
+ Ok(m) => {{
+ // SAFETY: No data race, since `__MOD` can only be accessed by this
+ // module and there only `__init` and `__exit` access it. These
+ // functions are only called once and `__exit` cannot be called
+ // before or during `__init`.
+ unsafe {{
+ __MOD = Some(m);
+ }}
+ return 0;
+ }}
+ Err(e) => {{
+ return e.to_errno();
+ }}
+ }}
+ }}
- fn __init() -> core::ffi::c_int {{
- match <{type_} as kernel::Module>::init(&THIS_MODULE) {{
- Ok(m) => {{
+ /// # Safety
+ ///
+ /// This function must
+ /// - only be called once,
+ /// - be called after `__init` has been called and returned `0`.
+ unsafe fn __exit() {{
+ // SAFETY: No data race, since `__MOD` can only be accessed by this module
+ // and there only `__init` and `__exit` access it. These functions are only
+ // called once and `__init` was already called.
unsafe {{
- __MOD = Some(m);
+ // Invokes `drop()` on `__MOD`, which should be used for cleanup.
+ __MOD = None;
}}
- return 0;
- }}
- Err(e) => {{
- return e.to_errno();
}}
- }}
- }}
- fn __exit() {{
- unsafe {{
- // Invokes `drop()` on `__MOD`, which should be used for cleanup.
- __MOD = None;
+ {modinfo}
}}
}}
-
- {modinfo}
",
type_ = info.type_,
name = info.name,