From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-m49197.qiye.163.com (mail-m49197.qiye.163.com [45.254.49.197]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EA1E030D3E8; Thu, 10 Sep 2026 05:51:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.254.49.197 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789019481; cv=none; b=E1Tfgt1Ch9GSc1rWhNHWWoMsq37yNe+rgpJoKlqCuJT+45my3iV58rE78tJrpdx9N8Px/NMcNLc00Am1AO0cp6a7e4pvmZhW/xUaJYxF8fNthNlkYyLflsuBgVYPw0SoUrDeqcrAa7YmA5H4eDnap1URvGlpY5FwmQNwveqiEgI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789019481; c=relaxed/simple; bh=sthCcF/sNcApycehZxI7ySnbqcrCrh0oGJyrDEjPzBQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=BlE8InLY35QESJRCMZhNg6z5HnRzkYzJGm7LmXoqWMI8uqp67KqMCIsJnhkEQG97Cm/rV4UAPlnhyNGaV7xg1Jw+G/9xinl8BQcNmOo9baib6dRm+vBLkouD+i/cnncyV0CQoZ6p+83Jjn+vYcgUtXXSGjXP+C1WSvuSRFA1Qe8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=stu.pku.edu.cn; spf=pass smtp.mailfrom=stu.pku.edu.cn; dkim=pass (1024-bit key) header.d=stu.pku.edu.cn header.i=@stu.pku.edu.cn header.b=Wj8YiKOP; arc=none smtp.client-ip=45.254.49.197 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=stu.pku.edu.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=stu.pku.edu.cn Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=stu.pku.edu.cn header.i=@stu.pku.edu.cn header.b="Wj8YiKOP" Received: from localhost.localdomain (unknown [106.120.124.5]) by smtp.qiye.163.com (Hmail) with ESMTP id 4d3b9ec9e; Thu, 10 Sep 2026 13:51:11 +0800 (GMT+08:00) From: Chunfeng Song To: Jakub Kicinski , "David S. Miller" , Eric Dumazet , Paolo Abeni Cc: netdev@vger.kernel.org, rust-for-linux@vger.kernel.org, Andrew Lunn , Heiner Kallweit , "Russell King (Oracle)" , Miguel Ojeda , Boqun Feng , Gary Guo , FUJITA Tomonori , Trevor Gross , stable@vger.kernel.org Subject: [PATCH net v6] rust: net: phy: fix off-by-one bit positions in device status accessors Date: Thu, 10 Sep 2026 05:51:10 +0000 Message-ID: <20260910055110.167110-1-springbreeze@stu.pku.edu.cn> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-HM-Tid: 0aa089debb8a03a1kunm6d76624b183ffd X-HM-MType: 10 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFITzdXWRgWCB1ZQUpXWS1ZQUlXWQ8JGhUIEh9ZQVlDHRgfVk0ZHkpDSh5KTkwZH1YeHw 5VEwETFhoSFyQUDg9ZV1kYEgtZQVlKS01VSklLVUpJT1VOWVdZFhoPEhUdFFlBWU9LSFVKS0hKTk xOVUpLS1VKQktLWQY+ DKIM-Signature: a=rsa-sha256; b=Wj8YiKOPXqB4zVdj+jjmflh7zDwuYvbPgBycoMa610oPr2BTqunN1MX93MDinxk9VOgDMOAraNmQC031He5O3n0HE2edhQPJ4ppVBDFDftexiTCDl/hAxNgVcrvYNXfu4GrgiOzRAlWN2PQUnYKq9JEnFn8DO0UAY8dW2cxxMHg=; c=relaxed/relaxed; s=default; d=stu.pku.edu.cn; v=1; bh=rhEO/9fD+Arvx5VJ3IVK2ueO7ZfQCkmPusDExwKpZFQ=; h=date:mime-version:subject:message-id:from; The hand-written bitfield offsets in is_link_up(), is_autoneg_enabled() and is_autoneg_completed() were correct when the abstraction was merged: at that time autoneg, link, and autoneg_complete were at bits 13, 14, and 15 of struct phy_device's first bitfield unit. Commit 2796ff1e3dca ("net: phy: add flag is_genphy_driven to struct phy_device") later inserted is_genphy_driven just before autoneg, shifting the three fields up by one, so the accessors now read: is_link_up() reads bit 14 = autoneg is_autoneg_enabled() reads bit 13 = is_genphy_driven is_autoneg_completed() reads bit 15 = link The official ax88796b Rust driver uses all three accessors in its read_status() implementation, so it inherits the bug. phy_attach_direct() sets is_genphy_driven only when it falls back to the generic driver, and ax88796b has a real driver, so is_genphy_driven stays 0. The broken is_autoneg_enabled() therefore reads bit 13 as 0, compares it against AUTONEG_ENABLE (1), and always returns false, so read_status() never reaches the resolve_aneg_linkmode() call. The ordinary bindgen accessors take &self. Calling them through (*phydev).link() would create a shared reference to the complete bindings::phy_device, which is not appropriate for an object wrapped in Opaque. Use the bindgen-generated raw accessors (link_raw(), autoneg_raw(), and autoneg_complete_raw()) instead. They retain the bit positions and endianness handling generated from the C layout without creating a Rust reference to the complete phy_device. Drop the hand-written numbers together with the TODO comment that marked them as a stopgap. The raw accessors are only emitted by bindgen 0.71 and later, and were added at the Rust-for-Linux project's request, so this fix can only be backported to stable branches whose minimum bindgen version is at least that, hence the scope on the Cc: stable line below. Found by a static equivalence audit (C2RustDrv, a C-to-Rust driver migration tool) that compares hand-written bitfield offsets against the bindgen layout of struct phy_device. Verified by building the bindings and checking the generated accessors; no runtime testing was possible without PHY hardware. Fixes: 2796ff1e3dca ("net: phy: add flag is_genphy_driven to struct phy_device") Cc: stable@vger.kernel.org # Only 7.1.y and later (requires bindgen's raw pointer accessors). Link: https://github.com/rust-lang/rust-bindgen/issues/2674 Signed-off-by: Chunfeng Song --- v6: - Name read_status() instead of the vague "link-change handling" in the commit message (FUJITA Tomonori). - Correct the impact description: on ax88796b, which has its own driver, is_genphy_driven stays 0, so the broken is_autoneg_enabled() always returns false and read_status() never reaches the resolve_aneg_linkmode() call (FUJITA Tomonori). - Rewrite the SAFETY comments to state why the raw accessors may be called: the pointer is valid and there is no concurrent write to the field (FUJITA Tomonori). v5: https://lore.kernel.org/r/20260901143251.136378-1-springbreeze@stu.pku.edu.cn/ - Move the comparison out of the `unsafe` block so that only the raw accessor call stays inside (Gary Guo, Miguel Ojeda). - Scope the `Cc: stable` backport to 7.1.y and later, since the raw accessors require bindgen 0.71 (Miguel Ojeda). - Mention the bindgen 0.71 dependency in the commit message. v4: https://lore.kernel.org/r/20260901031824.1377498-1-springbreeze@stu.pku.edu.cn/ - Use the bindgen-generated raw accessors to avoid creating a shared reference to the complete C `phy_device`, as suggested by Jakub Kicinski. - Update the SAFETY comments to describe pointer validity and the callback-context preconditions. - Add `#[inline]` to the three small forwarding methods. v3: https://lore.kernel.org/r/20260825111334.795732-1-springbreeze@stu.pku.edu.cn/ - Use the bindgen-generated accessors instead of hard-coded bit numbers. - Update the Fixes tag and add the net tree subject prefix. v2: https://lore.kernel.org/r/20260824111227.742645-1-springbreeze@stu.pku.edu.cn/ - Use bindgen-generated accessors as suggested by Andrew Lunn. - Explain that the offsets drifted after `is_genphy_driven` was added. v1: https://lore.kernel.org/r/20260823103644.342849-1-springbreeze@stu.pku.edu.cn/ rust/kernel/net/phy.rs | 38 ++++++++++++++++++-------------------- 1 file changed, 18 insertions(+), 20 deletions(-) diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs index 956cda573ddb..c4e7b1d6c6f4 100644 --- a/rust/kernel/net/phy.rs +++ b/rust/kernel/net/phy.rs @@ -123,39 +123,37 @@ pub fn state(&self) -> DeviceState { /// Gets the current link state. /// /// It returns true if the link is up. + #[inline] pub fn is_link_up(&self) -> bool { - const LINK_IS_UP: u64 = 1; - // TODO: the code to access to the bit field will be replaced with automatically - // generated code by bindgen when it becomes possible. - // SAFETY: The struct invariant ensures that we may access - // this field without additional synchronization. - let bit_field = unsafe { &(*self.0.get())._bitfield_1 }; - bit_field.get(14, 1) == LINK_IS_UP + let phydev = self.0.get().cast_const(); + // SAFETY: By the type invariant of `Device`, `phydev` points to a valid + // `struct phy_device`, and there is no concurrent write to this field. + let link = unsafe { bindings::phy_device::link_raw(phydev) }; + link == 1 } /// Gets the current auto-negotiation configuration. /// /// It returns true if auto-negotiation is enabled. + #[inline] pub fn is_autoneg_enabled(&self) -> bool { - // TODO: the code to access to the bit field will be replaced with automatically - // generated code by bindgen when it becomes possible. - // SAFETY: The struct invariant ensures that we may access - // this field without additional synchronization. - let bit_field = unsafe { &(*self.0.get())._bitfield_1 }; - bit_field.get(13, 1) == u64::from(bindings::AUTONEG_ENABLE) + let phydev = self.0.get().cast_const(); + // SAFETY: By the type invariant of `Device`, `phydev` points to a valid + // `struct phy_device`, and there is no concurrent write to this field. + let autoneg = unsafe { bindings::phy_device::autoneg_raw(phydev) }; + autoneg == bindings::AUTONEG_ENABLE } /// Gets the current auto-negotiation state. /// /// It returns true if auto-negotiation is completed. + #[inline] pub fn is_autoneg_completed(&self) -> bool { - const AUTONEG_COMPLETED: u64 = 1; - // TODO: the code to access to the bit field will be replaced with automatically - // generated code by bindgen when it becomes possible. - // SAFETY: The struct invariant ensures that we may access - // this field without additional synchronization. - let bit_field = unsafe { &(*self.0.get())._bitfield_1 }; - bit_field.get(15, 1) == AUTONEG_COMPLETED + let phydev = self.0.get().cast_const(); + // SAFETY: By the type invariant of `Device`, `phydev` points to a valid + // `struct phy_device`, and there is no concurrent write to this field. + let completed = unsafe { bindings::phy_device::autoneg_complete_raw(phydev) }; + completed == 1 } /// Sets the speed of the PHY. base-commit: 2709dd5ae32f0828f386327c76bba9f39f63a1c6 -- 2.43.0