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From:   "Andreas Hindborg (Samsung)" <nmi@metaspace.dk>
To:     Boqun Feng <boqun.feng@gmail.com>
Cc:     rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Gary Guo <gary@garyguo.net>,
        =?utf-8?Q?Bj=C3=B6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        Martin Rodriguez Reboredo <yakoyoku@gmail.com>,
        Alice Ryhl <aliceryhl@google.com>,
        Dariusz Sosnowski <dsosnowski@dsosnowski.pl>,
        Geoffrey Thomas <geofft@ldpreload.com>,
        Fox Chen <foxhlchen@gmail.com>,
        John Baublitz <john.m.baublitz@gmail.com>,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        Kees Cook <keescook@chromium.org>, stable@vger.kernel.org
Subject: Re: [PATCH 2/3] rust: allocator: Use krealloc_aligned() in
 KernelAllocator::alloc
Date:   Mon, 31 Jul 2023 10:48:57 +0200
In-reply-to: <20230730012905.643822-3-boqun.feng@gmail.com>
Message-ID: <873514qxd2.fsf@metaspace.dk>
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Boqun Feng <boqun.feng@gmail.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@gmail.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@samsung.com>