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Message-ID: <e4f7ae0c-5397-4b20-80e8-6c0baece3e8c@suse.cz>
Date:   Mon, 31 Jul 2023 09:56:20 +0200
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Subject: Re: [PATCH 1/3] rust: allocator: Prevent mis-aligned allocation
To:     Boqun Feng <boqun.feng@gmail.com>, rust-for-linux@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc:     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>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        Kees Cook <keescook@chromium.org>, stable@vger.kernel.org,
        Andreas Hindborg <nmi@metaspace.dk>
References: <20230730012905.643822-1-boqun.feng@gmail.com>
 <20230730012905.643822-2-boqun.feng@gmail.com>
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From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20230730012905.643822-2-boqun.feng@gmail.com>
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On 7/30/23 03:29, Boqun Feng wrote:
> Currently the rust allocator 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.
> 
> Fix 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 the 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@suse.cz>
> Co-developed-by: Andreas Hindborg (Samsung) <nmi@metaspace.dk>
> Signed-off-by: Andreas Hindborg (Samsung) <nmi@metaspace.dk>
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> Cc: stable@vger.kernel.org # v6.1+

Acked-by: Vlastimil Babka <vbabka@suse.cz>