This is a note to let you know that I've just added the patch titled
rust: arc: add explicit `drop()` around `Box::from_raw()`
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rust-arc-add-explicit-drop-around-box-from_raw.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 828176d037e29f813792a8b3ac1591834240e96f Mon Sep 17 00:00:00 2001
From: Miguel Ojeda <ojeda@xxxxxxxxxx>
Date: Wed, 23 Aug 2023 18:02:42 +0200
Subject: rust: arc: add explicit `drop()` around `Box::from_raw()`
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From: Miguel Ojeda <ojeda@xxxxxxxxxx>
commit 828176d037e29f813792a8b3ac1591834240e96f upstream.
`Box::from_raw()` is `#[must_use]`, which means the result cannot
go unused.
In Rust 1.71.0, this was not detected because the block expression
swallows the diagnostic [1]:
unsafe { Box::from_raw(self.ptr.as_ptr()) };
It would have been detected, however, if the line had been instead:
unsafe { Box::from_raw(self.ptr.as_ptr()); }
i.e. the semicolon being inside the `unsafe` block, rather than
outside.
In Rust 1.72.0, the compiler started warning about this [2], so
without this patch we will get:
error: unused return value of `alloc::boxed::Box::<T>::from_raw` that must be used
--> rust/kernel/sync/arc.rs:302:22
|
302 | unsafe { Box::from_raw(self.ptr.as_ptr()) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: call `drop(Box::from_raw(ptr))` if you intend to drop the `Box`
= note: `-D unused-must-use` implied by `-D warnings`
help: use `let _ = ...` to ignore the resulting value
|
302 | unsafe { let _ = Box::from_raw(self.ptr.as_ptr()); };
| +++++++ +
Thus add an add an explicit `drop()` as the `#[must_use]`'s
annotation suggests (instead of the more general help line).
Link: https://github.com/rust-lang/rust/issues/104253 [1]
Link: https://github.com/rust-lang/rust/pull/112529 [2]
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@xxxxxxxxx>
Reviewed-by: Gary Guo <gary@xxxxxxxxxxx>
Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
Reviewed-by: Andreas Hindborg <a.hindborg@xxxxxxxxxxx>
Reviewed-by: Björn Roy Baron <bjorn3_gh@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230823160244.188033-2-ojeda@xxxxxxxxxx
Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
rust/kernel/sync/arc.rs | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -302,7 +302,7 @@ impl<T: ?Sized> Drop for Arc<T> {
// The count reached zero, we must free the memory.
//
// SAFETY: The pointer was initialised from the result of `Box::leak`.
- unsafe { Box::from_raw(self.ptr.as_ptr()) };
+ unsafe { drop(Box::from_raw(self.ptr.as_ptr())) };
}
}
}
Patches currently in stable-queue which might be from ojeda@xxxxxxxxxx are
queue-6.6/rust-upgrade-to-rust-1.72.1.patch
queue-6.6/rust-task-remove-redundant-explicit-link.patch
queue-6.6/rust-upgrade-to-rust-1.73.0.patch
queue-6.6/rust-arc-add-explicit-drop-around-box-from_raw.patch
queue-6.6/rust-print-use-explicit-link-in-documentation.patch
