linux-kernel - Re: [PATCH 05/10] rust: xarray: use `xas_load` instead of `xa

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87eco1grin.fsf@t14s.mail-host-address-is-not-set>
Date: Wed, 07 Jan 2026 20:19:12 +0100
From: Andreas Hindborg <a.hindborg@...nel.org>
To: Tamir Duberstein <tamird@...il.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
 Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
 Björn Roy
 Baron <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>, Alice
 Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, Danilo
 Krummrich <dakr@...nel.org>, Daniel Gomez <da.gomez@...nel.org>,
 rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/10] rust: xarray: use `xas_load` instead of `xa_load`
 in `Guard::load`

Tamir Duberstein <tamird@...il.com> writes:

> On Wed, Dec 3, 2025 at 5:27 PM Andreas Hindborg <a.hindborg@...nel.org> wrote:
>>
>> Replace the call to `xa_load` with `xas_load` in `Guard::load`. The
>> `xa_load` function takes the XArray lock internally, which would cause
>> a double lock since the `Guard` already holds the lock.
>
> This is not correct. `xa_load` takes and releases the RCU lock only,
> not the XArray lock.

You are right. However, we do not need to take the RCU lock either in
this case, right?

>
>> The `xas_load`
>> function operates on XArray state and assumes the lock is already held,
>> which is the correct API to use when holding a `Guard`.
>>
>> This change also removes the `#[expect(dead_code)]` annotation from
>> `XArrayState` and its constructor, as they are now in use.
>>
>> Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
>> ---
>>  rust/kernel/xarray.rs | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/rust/kernel/xarray.rs b/rust/kernel/xarray.rs
>> index f6e610b059625..0f69a523b72bf 100644
>> --- a/rust/kernel/xarray.rs
>> +++ b/rust/kernel/xarray.rs
>> @@ -215,8 +215,10 @@ fn load<F, U>(&self, index: usize, f: F) -> Option<U>
>>      where
>>          F: FnOnce(NonNull<c_void>) -> U,
>>      {
>> -        // SAFETY: `self.xa.xa` is always valid by the type invariant.
>> -        let ptr = unsafe { bindings::xa_load(self.xa.xa.get(), index) };
>> +        let mut state = XArrayState::new(self, index);
>> +        // SAFETY: `state.state` is always valid by the type invariant of
>> +        // `XArrayState`.
>> +        let ptr = unsafe { bindings::xas_load(&raw mut state.state) };
>
> Can this be a method on XArrayState?

OK.


Best regards,
Andreas Hindborg