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Sat, 5 Sep 2026 20:47:23 +0200 (CEST) From: Markus Probst Date: Sat, 05 Sep 2026 18:47:24 +0000 Subject: [PATCH v4] rust: serdev: Mitigate race conditions Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260905-rust_serdev_fix-v4-1-31e1bbcc0c00@posteo.de> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/4WOy27CMBREfyXyuhf5EZuEFf+BKuTHdXElMNiO1 Qrl32sCC0QXLGc0Z2auJGMKmMmmu5KENeQQT030Hx2xB336QgiuacIpV3SkPaQpl32DHNa9Dz9 gUHg/2kFLHEijzgmbvTTuPu86T+YbbbnVPBIJL1ObKvcYMToj2Hg8hrLp6nolIFlGbvQh5BLT7 3KvsiX8eCL/PakMGHDUIzdM9lqZ7TnmgnHlcOmq/A3PgYKQzltHFXqOr7x4w4u2bwZFpbLCr3X /zM/z/AfPJO0LbAEAAA== X-Change-ID: 20260904-rust_serdev_fix-be3ff9c8a5e8 To: Miguel Ojeda , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , =?utf-8?q?Onur_=C3=96zkan?= , Greg Kroah-Hartman Cc: linux-serial@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Sashiko Bot , Markus Probst X-Developer-Signature: v=1; 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preference=encrypt There are currently 2 race conditions: - in probe if `Driver::probe` returns Err - in unbind . In those cases the driver data will be set to NULL before the serdev device was closed. If data is received while the driver data is dropped, the `receive_buf_callback` might try to access the `active` mutex on a null pointer. The race conditions can only occur if `Driver::receive` is implemented. The issue cannot be cleanly fixed without rewriting some logic, which might introduce new regressions. Temporarily disable the use of `Driver::receive`, until fixed in the next release. Fixes: 99f59aa82341 ("rust: add basic serial device bus abstractions") Reported-by: Sashiko Bot Closes: https://lore.kernel.org/linux-serial/20260905000836.C8FC91F00A3D@smtp.kernel.org/ Closes: https://lore.kernel.org/linux-serial/20260903222159.70A911F000E9@smtp.kernel.org/ Signed-off-by: Markus Probst --- I will submit a patch (for the next merge cycle) soon, which will address this issue and make the probe and unbind code less convoluted. --- Changes in v4: - remove comments - Link to v3: https://patch.msgid.link/20260905-rust_serdev_fix-v3-1-b86056c3f7a4@posteo.de Changes in v3: - mitigate it - Link to v2: https://patch.msgid.link/20260905-rust_serdev_fix-v2-0-35dfcd06ef2e@posteo.de Changes in v2: - also fix race condition on unbind - Link to v1: https://patch.msgid.link/20260905-rust_serdev_fix-v1-1-2ea92b154a6b@posteo.de --- rust/kernel/serdev.rs | 6 +++--- samples/rust/rust_driver_serdev.rs | 13 +------------ 2 files changed, 4 insertions(+), 15 deletions(-) diff --git a/rust/kernel/serdev.rs b/rust/kernel/serdev.rs index 17ca504b7f8d..f4c0f43b5273 100644 --- a/rust/kernel/serdev.rs +++ b/rust/kernel/serdev.rs @@ -148,9 +148,8 @@ fn drop(self: Pin<&mut Self>) { impl Adapter { const OPS: &'static bindings::serdev_device_ops = &bindings::serdev_device_ops { - receive_buf: if T::HAS_RECEIVE { - Some(Self::receive_buf_callback) - } else { + receive_buf: { + const_assert!(!T::HAS_RECEIVE); None }, write_wakeup: Some(bindings::serdev_device_write_wakeup), @@ -233,6 +232,7 @@ extern "C" fn remove_callback(sdev: *mut bindings::serdev_device) { T::unbind(sdev, data_pinned); } + #[expect(dead_code)] extern "C" fn receive_buf_callback( sdev: *mut bindings::serdev_device, buf: *const u8, diff --git a/samples/rust/rust_driver_serdev.rs b/samples/rust/rust_driver_serdev.rs index 51b4898cd855..3fd3eef15371 100644 --- a/samples/rust/rust_driver_serdev.rs +++ b/samples/rust/rust_driver_serdev.rs @@ -4,10 +4,7 @@ use kernel::{ acpi, - device::{ - Bound, - Core, // - }, + device::Core, of, prelude::*, serdev, @@ -60,14 +57,6 @@ fn probe<'bound>( Ok(Self { sdev: sdev.into() }) } - - fn receive<'bound>( - sdev: &'bound serdev::Device, - _this: Pin<&Self>, - data: &[u8], - ) -> usize { - sdev.write(data).unwrap_or_default() as usize - } } impl Drop for SampleDriver { --- base-commit: e5e04726cdd043e309677071ab1b65a4b18f422b change-id: 20260904-rust_serdev_fix-be3ff9c8a5e8