linux-kernel - Re: [PATCH 1/3] rust: allocator: Prevent mis-aligned allocation

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Date:   Sun, 30 Jul 2023 15:53:57 -0700
From:   Boqun Feng <boqun.feng@...il.com>
To:     Björn Roy Baron <bjorn3_gh@...tonmail.com>
Cc:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        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>,
        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,
        Andreas Hindborg <nmi@...aspace.dk>
Subject: Re: [PATCH 1/3] rust: allocator: Prevent mis-aligned allocation

On Sun, Jul 30, 2023 at 10:41:54PM +0000, Björn Roy Baron wrote:
> On Jul 30, 2023, 10:43 PM, Miguel Ojeda < miguel.ojeda.sandonis@...il.com> wrote:
> > On Sun, Jul 30, 2023 at 3:29 AM Boqun > Feng <boqun.feng@...il.com> wrote:
> > >
> > > +// Note: Although these are *safe* functions, but they are only generated at
> > > +// `GlobalAlloc` callsites, hence we assume the parameters obey the same
> > > +// `GlobalAlloc` function safety requirements: size and align should form a
> > > +// valid layout, and size is greater than 0.
> >
> > Thanks for adding all the `// SAFETY` comments here Boqun!
> >
> > Björn, do they look good to you? (since you fixed the issue in the compiler)
> 
> Based on a quick look, yes. The __rust_* methods that are normally generated by the compiled directly jump to the respective global allocator method, so they have the same safety requirements.
> 

Good to know, thanks!

> >
> > On this comment in particular, "generated at `GlobalAlloc` callsites"
> sounds a bit confusing to me. Would "... called by the compiler with
> parameters that obey ..." make sense? Or does the sentence refer to

Agreed. It's better. So reword as below:

// Note: Although these are *safe* functions, but they are called by the
// compiler with the parameters that obey the same `GlobalAlloc`
// function safety requirements: size and align should form a valid
// layout, and size is greater than 0.

Regards,
Boqun

> the normal case (i.e. when the functions are generated)? Anyway, it is
> not a big deal.
> >
> > Cheers,
> > Miguel
> 
> Cheers,
> Björn
> 
> (resent as I accidentally sent html instead of plain text)