linux-kernel - Re: [PATCH 2/3] rust: allocator: Use krealloc

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Message-ID: <873514qxd2.fsf@metaspace.dk>
Date:   Mon, 31 Jul 2023 10:48:57 +0200
From:   "Andreas Hindborg (Samsung)" <nmi@...aspace.dk>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Benno Lossin <benno.lossin@...ton.me>,
        Martin Rodriguez Reboredo <yakoyoku@...il.com>,
        Alice Ryhl <aliceryhl@...gle.com>,
        Dariusz Sosnowski <dsosnowski@...snowski.pl>,
        Geoffrey Thomas <geofft@...reload.com>,
        Fox Chen <foxhlchen@...il.com>,
        John Baublitz <john.m.baublitz@...il.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Kees Cook <keescook@...omium.org>, stable@...r.kernel.org
Subject: Re: [PATCH 2/3] rust: allocator: Use krealloc_aligned() in
 KernelAllocator::alloc


Boqun Feng <boqun.feng@...il.com> writes:

> This fixes the potential issue that when KernelAllocator is used, the
> allocation may be mis-aligned due to SLAB's alignment guarantee.
>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> ---
>  rust/kernel/allocator.rs | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/rust/kernel/allocator.rs b/rust/kernel/allocator.rs
> index fae11d1fdba7..1aec688cf0e0 100644
> --- a/rust/kernel/allocator.rs
> +++ b/rust/kernel/allocator.rs
> @@ -41,9 +41,9 @@ unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: bindings::gf
>  
>  unsafe impl GlobalAlloc for KernelAllocator {
>      unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
> -        // `krealloc()` is used instead of `kmalloc()` because the latter is
> -        // an inline function and cannot be bound to as a result.
> -        unsafe { bindings::krealloc(ptr::null(), layout.size(), bindings::GFP_KERNEL) as *mut u8 }
> +        // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
> +        // requirement.
> +        unsafe { krealloc_aligned(ptr::null_mut(), layout, bindings::GFP_KERNEL) }
>      }
>  
>      unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {

Reviewed-by: Andreas Hindborg <a.hindborg@...sung.com>