linux-kernel - Re: [PATCH] rust: allocator: Prevents mis-aligned allocation

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Message-ID: <d31dac7e-671a-1741-5f13-c61624bceac0@ryhl.io>
Date:   Tue, 13 Jun 2023 22:38:12 +0200
From:   Alice Ryhl <alice@...l.io>
To:     Boqun Feng <boqun.feng@...il.com>, rust-for-linux@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     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>,
        Andreas Hindborg <nmi@...aspace.dk>, stable@...r.kernel.org
Subject: Re: [PATCH] rust: allocator: Prevents mis-aligned allocation

On 6/13/23 18:42, Boqun Feng wrote:
> Currently the KernelAllocator simply passes the size of the type Layout
> to krealloc(), and in theory the alignment requirement from the type
> Layout may be larger than the guarantee provided by SLAB, which means
> the allocated object is mis-aligned.
> 
> Fixes this by adjusting the allocation size to the nearest power of two,
> which SLAB always guarantees a size-aligned allocation. And because Rust
> guarantees that original size must be a multiple of alignment and the
> alignment must be a power of two, then the alignment requirement is
> satisfied.
> 
> Suggested-by: Vlastimil Babka <vbabka@...e.cz>
> Co-developed-by: Andreas Hindborg (Samsung) <nmi@...aspace.dk>
> Signed-off-by: Andreas Hindborg (Samsung) <nmi@...aspace.dk>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> Cc: stable@...r.kernel.org # v6.1+

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>