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From:   Dennis Dai <dzy.0424thu@gmail.com>
Date:   Thu, 3 Nov 2022 14:12:43 +0800
Message-ID: <CACMswuMVERF_+R3Qxb0xGHCBQUCuxtBLA+eDo__Coed3BoVC3A@mail.gmail.com>
Subject: rust nvme driver: potential sleep-in-atomic-context
To:     Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@google.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org
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The rust nvme driver [1] (which is still pending to be merged into
mainline [2]) has a potential sleep-in-atomic-context bug.

The potential buggy code is below

    // drivers/block/nvme.rs:192
    dev.queues.lock().io.try_reserve(nr_io_queues as _)?;
    // drivers/block/nvme.rs:227
    dev.queues.lock().io.try_push(io_queue.clone())?;

The queues field is wrapped in SpinLock, which means that we cannot
sleep (or indirectly call any function that may sleep) when the lock
is held.
However try_reserve function may indirectly call krealloc with a
sleepable flag GFP_KERNEL (that's default behaviour of the global rust
allocator).
The the case is similar for try_push.

I wonder if the bug could be confirmed.


[1] https://github.com/metaspace/rust-linux/commit/d88c3744d6cbdf11767e08bad56cbfb67c4c96d0
[2] https://lore.kernel.org/lkml/202210010816.1317F2C@keescook/