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Sat, 5 Sep 2026 20:32:57 +0200 (CEST) From: Markus Probst Date: Sat, 05 Sep 2026 18:33:00 +0000 Subject: [PATCH v3] rust: serdev: Mitigate race conditions Precedence: bulk X-Mailing-List: rust-for-linux@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-v3-1-b86056c3f7a4@posteo.de> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/4WOyw7CIBBFf6Vh7RigD21X/ocxhsegmFgqUKIx/ XdpdWHiwuWd3HPnPElAbzGQrngSj8kG6/ocylVB1Fn0JwSrcyac8oa2tAI/hnjMkMZ0NPYOEkt jWrUVNW5JpgaP+bws7g/vHEZ5QRXnmU/D423Mr+K7RqQICMpdrzZ2RdqsS/CKkZk+2xCdfyx6i S3lj0n9Y5IYMOAoWi5ZXYlG7gYXIrq1xmUr8T88BwplrY3StEHD8ZufpukFJjvJ+SwBAAA= 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 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 | 7 ++++++- samples/rust/rust_driver_serdev.rs | 6 +++--- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/rust/kernel/serdev.rs b/rust/kernel/serdev.rs index 17ca504b7f8d..63b489404558 100644 --- a/rust/kernel/serdev.rs +++ b/rust/kernel/serdev.rs @@ -148,10 +148,14 @@ 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 { + /* receive_buf: if T::HAS_RECEIVE { Some(Self::receive_buf_callback) } else { None + }, */ + receive_buf: { + const_assert!(!T::HAS_RECEIVE); + None }, write_wakeup: Some(bindings::serdev_device_write_wakeup), }; @@ -233,6 +237,7 @@ 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..863db75d3b5a 100644 --- a/samples/rust/rust_driver_serdev.rs +++ b/samples/rust/rust_driver_serdev.rs @@ -5,7 +5,7 @@ use kernel::{ acpi, device::{ - Bound, + // Bound, Core, // }, of, @@ -61,13 +61,13 @@ fn probe<'bound>( Ok(Self { sdev: sdev.into() }) } - fn receive<'bound>( + /*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