From 97b281d7edb2ae662365be2809cd728470119720 Mon Sep 17 00:00:00 2001 From: Philipp Stanner Date: Mon, 16 Feb 2026 14:16:15 +0100 Subject: [PATCH] rust: list: Add unsafe blocks for container_of and safety comments impl_list_item_mod.rs calls container_of! without unsafe blocks at a couple of places. Since container_of! is unsafe, the blocks are strictly necessary. The problem was so far not visible because the "unsafe-op-in-unsafe-fn" check is a lint rather than a hard compiler error, and Rust suppresses lints triggered inside of a macro from another crate. Thus, the error becomes only visible once someone from within the kernel crate tries to use linked lists: error[E0133]: call to unsafe function `core::ptr::mut_ptr::::byte_sub` is unsafe and requires unsafe block --> rust/kernel/lib.rs:252:29 | 252 | let container_ptr = field_ptr.byte_sub(offset).cast::<$Container>(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function | ::: rust/kernel/drm/jq.rs:98:1 | 98 | / impl_list_item! { 99 | | impl ListItem<0> for BasicItem { using ListLinks { self.links }; } 100 | | } | |_- in this macro invocation | note: an unsafe function restricts its caller, but its body is safe by default --> rust/kernel/list/impl_list_item_mod.rs:216:13 | 216 | unsafe fn view_value(me: *mut $crate::list::ListLinks<$num>) -> *const Self { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ::: rust/kernel/drm/jq.rs:98:1 | 98 | / impl_list_item! { 99 | | impl ListItem<0> for BasicItem { using ListLinks { self.links }; } 100 | | } | |_- in this macro invocation = note: requested on the command line with `-D unsafe-op-in-unsafe-fn` = note: this error originates in the macro `$crate::container_of` which comes from the expansion of the macro `impl_list_item` Therefore, add unsafe blocks to container_of! calls to fix the issue. [ As discussed, let's fix the build for those that want to use the macro within the `kernel` crate now and we can discuss the proper safety comments afterwards. Thus I removed the ones from the patch. However, we cannot just avoid the comments with `CLIPPY=1`, so I provided placeholders for now, like we did in the past. They were also needed for an `unsafe impl`. While I am not happy about it, it isn't worse than the current status (the comments were meant to be there), and at least this shows what is missing -- our pre-existing "good first issue" [1] may motivate new contributors to complete them properly. Finally, I moved one of the existing safety comments one line down so that Clippy could locate it. Link: https://github.com/Rust-for-Linux/linux/issues/351 [1] - Miguel ] Cc: stable@vger.kernel.org Fixes: c77f85b347dd ("rust: list: remove OFFSET constants") Suggested-by: Alice Ryhl Signed-off-by: Philipp Stanner Reviewed-by: Gary Guo Reviewed-by: Alice Ryhl Link: https://patch.msgid.link/20260216131613.45344-3-phasta@kernel.org [ Fixed formatting. Reworded to fix the lint suppression explanation. Indent build error. - Miguel ] Signed-off-by: Miguel Ojeda --- rust/kernel/list/impl_list_item_mod.rs | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) diff --git a/rust/kernel/list/impl_list_item_mod.rs b/rust/kernel/list/impl_list_item_mod.rs index 202bc6f97c13..ee53d0387e63 100644 --- a/rust/kernel/list/impl_list_item_mod.rs +++ b/rust/kernel/list/impl_list_item_mod.rs @@ -84,11 +84,12 @@ macro_rules! impl_has_list_links_self_ptr { // right type. unsafe impl$(<$($generics)*>)? $crate::list::HasSelfPtr<$item_type $(, $id)?> for $self {} + // SAFETY: TODO. unsafe impl$(<$($generics)*>)? $crate::list::HasListLinks$(<$id>)? for $self { #[inline] unsafe fn raw_get_list_links(ptr: *mut Self) -> *mut $crate::list::ListLinks$(<$id>)? { - // SAFETY: The caller promises that the pointer is not dangling. let ptr: *mut $crate::list::ListLinksSelfPtr<$item_type $(, $id)?> = + // SAFETY: The caller promises that the pointer is not dangling. unsafe { ::core::ptr::addr_of_mut!((*ptr)$(.$field)*) }; ptr.cast() } @@ -217,7 +218,7 @@ macro_rules! impl_list_item { // SAFETY: `me` originates from the most recent call to `prepare_to_insert`, so it // points at the field `$field` in a value of type `Self`. Thus, reversing that // operation is still in-bounds of the allocation. - $crate::container_of!(me, Self, $($field).*) + unsafe { $crate::container_of!(me, Self, $($field).*) } } // GUARANTEES: @@ -242,7 +243,7 @@ macro_rules! impl_list_item { // SAFETY: `me` originates from the most recent call to `prepare_to_insert`, so it // points at the field `$field` in a value of type `Self`. Thus, reversing that // operation is still in-bounds of the allocation. - $crate::container_of!(me, Self, $($field).*) + unsafe { $crate::container_of!(me, Self, $($field).*) } } } )*}; @@ -270,9 +271,12 @@ macro_rules! impl_list_item { // SAFETY: The caller promises that `me` points at a valid value of type `Self`. let links_field = unsafe { >::view_links(me) }; - let container = $crate::container_of!( - links_field, $crate::list::ListLinksSelfPtr, inner - ); + // SAFETY: TODO. + let container = unsafe { + $crate::container_of!( + links_field, $crate::list::ListLinksSelfPtr, inner + ) + }; // SAFETY: By the same reasoning above, `links_field` is a valid pointer. let self_ptr = unsafe { @@ -319,9 +323,12 @@ macro_rules! impl_list_item { // `ListArc` containing `Self` until the next call to `post_remove`. The value cannot // be destroyed while a `ListArc` reference exists. unsafe fn view_value(links_field: *mut $crate::list::ListLinks<$num>) -> *const Self { - let container = $crate::container_of!( - links_field, $crate::list::ListLinksSelfPtr, inner - ); + // SAFETY: TODO. + let container = unsafe { + $crate::container_of!( + links_field, $crate::list::ListLinksSelfPtr, inner + ) + }; // SAFETY: By the same reasoning above, `links_field` is a valid pointer. let self_ptr = unsafe { -- 2.47.3