From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f49.google.com (mail-pj1-f49.google.com [209.85.216.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3F3252750E4 for ; Wed, 30 Apr 2025 19:57:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.49 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746043025; cv=none; b=rfBod3A+yXcFoaJJLI+0JsdVpM7vNXIynTvkzh3+iAaqcxTlHy4hsvhqaZOPMhgsBkZaMm8xT55ng/N3ZHQvvs46V5MbOd3Tl7XE7o+6QfzoYZ+XO6ya5lCe9m7RhWUbXp47a4S3UJxsmw/FOHoFNrAW5YNH93iKICwNXXwwejk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746043025; c=relaxed/simple; bh=3qDTN+MBFQnDotoSGCXSC0TIqshMNt8VgM+VnIIfAOA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Cw5VPcrXoiKQL5Enuqu5PFCn3Q/WgV/N6KC4V+8RbuUTuWM4uc70Pi1Si9WCgKAhKpjGJKLQan29e4iD481f/bgLDN7QeKpGA4dW2P5Eg4q23C5Q8360j5g4yjhfXFdG3Ods46nVFqIm9nFITmIl9tII/UGFSK2EwyYoJCsx41w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=m1fTK7sW; arc=none smtp.client-ip=209.85.216.49 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="m1fTK7sW" Received: by mail-pj1-f49.google.com with SMTP id 98e67ed59e1d1-2ff799d99dcso321381a91.1 for ; Wed, 30 Apr 2025 12:57:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1746043022; x=1746647822; darn=lists.linux.dev; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=c+qKL+MUCJJ9XsZqOZSeMflU/a6s+djka0YUBDd9w14=; b=m1fTK7sWzWfqXh9lXRreK3/qaEPPnn41opNvzAI7oLiD/C7iF8oIErKghN4kdlTgyd Ub/lWr/oeo4Fh/0jhgnCRMbivf+7vL7GbDZvHvCNITId9YeYHP5Y+0qh1QeQqHAqWlYD MEjXZGh01kBK+vmqZZ0hMDaSJ9o7E1OaY5sp9Lpj1lN7YCx0IQuF50kfqDI8ovSiiiEJ Yv09591R8/PCt65t/5lA+6Bw82GcPKfFrrKhUqrdcFqJbLPyZzHzvRyQ2Suv3JHMMkVs lAuUt0amSmbVvb1oWZzxiQSuAsPvCtO280auECFRuP1pyhbpv3m1R3rnELpraxa/G4Le C+UQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1746043022; x=1746647822; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=c+qKL+MUCJJ9XsZqOZSeMflU/a6s+djka0YUBDd9w14=; b=AZ7+PtrLdT9t9raXCLsOMt64uILUnQspX+dzQv+IcVlhGq7HaJEule5X50psfeRMf2 uStByypmwO24OTbL3AHgtPwlizCs9rpQaZVt7khDfs0RKE3/qsYggwClL1Fx9UeaxF/a al9KsfEi7C9cj298qFlaHkLugzyPm+gQr77Ha9lvpDENgBGHz+rd5RX2ZKBEYP2I1+ny IiZGG3DWiSkvTPJq3DhB1akeZZNvagCr2w4UrTGqdEbKo5Sm79w7icxfwhsGUT/TPdrc JlznSmKlxWyIrmrr3I1gvsCkgqGv4yhu4pbBZbi1B8CX7cYAKg5RqulCOVJba1FDfl6w BshQ== X-Forwarded-Encrypted: i=1; AJvYcCW1frXbMxHGLYWtvmA0NhHR6//o7wwX/EwhyNUgZ1cfid0nfQhLvitvVEKQSA7kcXpiePF0pA==@lists.linux.dev X-Gm-Message-State: AOJu0YxhGJpaVvu7sGFYHxBQO1k8uaaE7JOcuJP6KRGA2Kh/9AR+GXrb xOYmOsXdG8MXOT3PGmRJtuXfCUFFH15Iva5zYkO+2MP+6z5Fnznb3vXW6ys32g== X-Gm-Gg: ASbGncsbibVRuteZ/YIsy/JS+KSjxG5KaAqe6GWkcDmD9Q932xzx/t/tk/hmE0fBYRY ttz9WEZ4DYegg+s0axcHchLNN0PCibap/o10l4siCc6rD7GmqeSrxpQhXr219gGgU4hoaEnK1iR 09zfmES+jfz+N86SDwjNQUBQpMcmk2Jo7lno6b8XZ7X7cUyKAsknbZABZuA6l4iFXqzHw45nImf ASrJDwwkaggLrGc08l5jrHf23zM9zarTqhIKK9SkHoxfWj4eJ0YE2np4eOhBB+8QDQiqoENGC/t Imv+P7nhjkmOwNI4+ygmwStJfygzKLPbHvWXcNZzf4MrjmtcTwOaMfRkgXYK54ArnmP3KWs7ArU c3/Cztg== X-Google-Smtp-Source: AGHT+IFYLwXsSVzpZ58dXpoeXLiC5qkI9bTIycsk32TydeZra3btf6V9VE3JspqpRKaeMTjXf206sg== X-Received: by 2002:a17:90b:3812:b0:2fe:b016:a6ac with SMTP id 98e67ed59e1d1-30a41e6c2fdmr10756a91.15.1746043022099; Wed, 30 Apr 2025 12:57:02 -0700 (PDT) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-30a3471ee7esm2100393a91.4.2025.04.30.12.57.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Apr 2025 12:57:01 -0700 (PDT) Date: Wed, 30 Apr 2025 12:56:57 -0700 From: William McVicker To: Robin Murphy Cc: joro@8bytes.org, will@kernel.org, Bjorn Helgaas , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Subject: Re: [PATCH] PCI: Fix driver_managed_dma check Message-ID: References: <20250425133929.646493-4-robin.murphy@arm.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250425133929.646493-4-robin.murphy@arm.com> On 04/25/2025, Robin Murphy wrote: > 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. Thanks! Reviewed-by: Will McVicker > > Reported-by: Will McVicker > Fixes: bcb81ac6ae3c ("iommu: Get DT/ACPI parsing into the proper probe path") > Signed-off-by: Robin Murphy > --- > 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 = to_pci_driver(dev->driver); > + const struct device_driver *drv = READ_ONCE(dev->driver); > struct device *bridge; > int ret = 0; > > @@ -1651,8 +1651,8 @@ static int pci_dma_configure(struct device *dev) > > pci_put_host_bridge_device(bridge); > > - /* @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 = iommu_device_use_default_domain(dev); > if (ret) > arch_teardown_dma_ops(dev); > -- > 2.39.2.101.g768bb238c484.dirty >