From nobody Sun Feb 8 00:40:15 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id ADE0C25A2CC; Fri, 25 Apr 2025 13:39:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745588390; cv=none; b=bUPWZrk5rSHpexsdQptUS1uzR8zd9K0VJQvjXhnuePttBZSVHGIkN/BDncHE53BwAfZZrGruIv41yfutLabxdX1H32gD7kmbbciDyDlDkanlbyVOUtv3wa3bbENpCII9BX6DPeQPKKYCinR0FG+Tirp+hGqBQe32SUBxALbFUUw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745588390; c=relaxed/simple; bh=dqb8vZ0QzGl1lb+a6KWe7g4pKVohHseW5ueItvPNZzI=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=JzvN37PRg4kU9E1MgXkeU/rvAT5TVLXaB53NL8WGbue47ylqDDdClRw+/qUU28LpUJzdSGPyFUnlMsnqQMSAIsW0yiL5yooYvmQoBZoxfq/SvnVogFxc2rbTx0yNv5uTvCS0KwyFhiyJi6W+diabX5yCPNH6MkRumE5ZjphOsVk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id EDC8D1A2D; Fri, 25 Apr 2025 06:39:42 -0700 (PDT) Received: from e121345-lin.cambridge.arm.com (e121345-lin.cambridge.arm.com [10.1.196.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 3EBA13F59E; Fri, 25 Apr 2025 06:39:47 -0700 (PDT) From: Robin Murphy To: joro@8bytes.org, will@kernel.org, Bjorn Helgaas Cc: iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Will McVicker Subject: [PATCH] PCI: Fix driver_managed_dma check Date: Fri, 25 Apr 2025 14:39:29 +0100 Message-Id: <20250425133929.646493-4-robin.murphy@arm.com> X-Mailer: git-send-email 2.39.2.101.g768bb238c484.dirty Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Since it's not currently safe to take device_lock() in the IOMMU probe path, that can race against really_probe() setting dev->driver before attempting to bind. The race itself isn't so bad, since we're only concerned with dereferencing dev->driver itself anyway, but sadly my attempt to implement the check with minimal churn leads to a kind of TOCTOU issue, where dev->driver becomes valid after to_pci_driver(NULL) is already computed, and thus the check fails to work as intended. Will and I both hit this with the platform bus, but the pattern here is the same, so fix it for correctness too. Reported-by: Will McVicker Fixes: bcb81ac6ae3c ("iommu: Get DT/ACPI parsing into the proper probe path= ") Signed-off-by: Robin Murphy Reviewed-by: Will McVicker --- drivers/pci/pci-driver.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index c8bd71a739f7..66e3bea7dc1a 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -1634,7 +1634,7 @@ static int pci_bus_num_vf(struct device *dev) */ static int pci_dma_configure(struct device *dev) { - struct pci_driver *driver =3D to_pci_driver(dev->driver); + const struct device_driver *drv =3D READ_ONCE(dev->driver); struct device *bridge; int ret =3D 0; =20 @@ -1651,8 +1651,8 @@ static int pci_dma_configure(struct device *dev) =20 pci_put_host_bridge_device(bridge); =20 - /* @driver may not be valid when we're called from the IOMMU layer */ - if (!ret && dev->driver && !driver->driver_managed_dma) { + /* @drv may not be valid when we're called from the IOMMU layer */ + if (!ret && drv && !to_pci_driver(drv)->driver_managed_dma) { ret =3D iommu_device_use_default_domain(dev); if (ret) arch_teardown_dma_ops(dev); --=20 2.39.2.101.g768bb238c484.dirty