From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 0B10338DD8; Tue, 6 Aug 2024 20:01:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722974462; cv=none; b=uiawXHNKnnhZT7wnYgkpmKN2BXI7fMxxgXSM89ScUMlW3Hzy6Oa7FZTOfrvCAsDKV4tUK2Q0PBYTvdHkLNlQMIhMayM7eRwcenNEEts8nhogVE2nF36dt9S7MW+BleNbehbZrY7TapZWojy62nm1nE9KMhau7Fn3N3++EzCksJY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722974462; c=relaxed/simple; bh=t/hN2y1XYKOsn2IY/TkVfglq3EKviiTjFSjUkFXXSXA=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=d7w3gccldK/LY/prCr/NSh+uBPkkgw7Ete5TXNDBFeTjn9s3DENRI9WCrl5XhfKs97jFekX0HTbOgB7XYV+EPvt3U/U8AA1c641V8ht/1SiOZaNrhspFqx5apK3kFENdn+L37xwOQJFpxIr+804GUWp31ORKULtZ5itsZwElaCY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YirUaony; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YirUaony" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 54973C4AF0C; Tue, 6 Aug 2024 20:01:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722974461; bh=t/hN2y1XYKOsn2IY/TkVfglq3EKviiTjFSjUkFXXSXA=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=YirUaonym+NqN0rn16gxCaQZnUdURBfBbcCtm04Th4BJn6KIoX/5HL8SMT0Ani+tV 3Z9Z48AFin+sbKkc6+MdfBdBuWxqCGysVXgsHafFmqh9n1gi2iPEnyTbuT0gWPx5tK Dj0rjzr4MMd4FRrRU9ePNjJrRDRL/hmHk5VDzemdUNxHPzRcJ5iVoa2uHb8Lgkw1NF 2rZlSRWiCHINPSFjKBxWVYYp5JOS7G1lpmrZ+gEh+RifTI/GzNEDCtc5wXeE59BpXC 5J51YO0gLxSo0r5h/JXKyUmK2Rca8+IZNyfIoBXMrb8ID2Pg/UdEnkbJH3Kj/WS81k gEHnuoZcQSURA== Date: Tue, 6 Aug 2024 15:00:59 -0500 From: Bjorn Helgaas To: Amit Machhiwal , Rob Herring Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, Bjorn Helgaas , Lizhi Hou , Saravana Kannan , Vaibhav Jain , Nicholas Piggin , Michael Ellerman , Vaidyanathan Srinivasan , Kowshik Jois B S , Lukas Wunner , kernel-team@lists.ubuntu.com, Stefan Bader Subject: Re: [PATCH v3] PCI: Fix crash during pci_dev hot-unplug on pseries KVM guest Message-ID: <20240806200059.GA74866@bhelgaas> 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-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240802183327.1309020-1-amachhiw@linux.ibm.com> On Sat, Aug 03, 2024 at 12:03:25AM +0530, Amit Machhiwal wrote: > With CONFIG_PCI_DYNAMIC_OF_NODES [1], a hot-plug and hot-unplug sequence > of a PCI device attached to a PCI-bridge causes following kernel Oops on > a pseries KVM guest: What is unique about pseries here? There's nothing specific to pseries in the patch, so I would expect this to be a generic problem on any arch. > RTAS: event: 2, Type: Hotplug Event (229), Severity: 1 > Kernel attempted to read user page (10ec00000048) - exploit attempt? (uid: 0) > BUG: Unable to handle kernel data access on read at 0x10ec00000048 Weird address. I would expect NULL or something. Where did this non-NULL pointer come from? > Faulting instruction address: 0xc0000000012d8728 > Oops: Kernel access of bad area, sig: 11 [#1] > LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries > > NIP [c0000000012d8728] __of_changeset_entry_invert+0x10/0x1ac > LR [c0000000012da7f0] __of_changeset_revert_entries+0x98/0x180 > Call Trace: > [c00000000bcc3970] [c0000000012daa60] of_changeset_revert+0x58/0xd8 > [c00000000bcc39c0] [c000000000d0ed78] of_pci_remove_node+0x74/0xb0 > [c00000000bcc39f0] [c000000000cdcfe0] pci_stop_bus_device+0xf4/0x138 > [c00000000bcc3a30] [c000000000cdd140] pci_stop_and_remove_bus_device_locked+0x34/0x64 > [c00000000bcc3a60] [c000000000cf3780] remove_store+0xf0/0x108 > [c00000000bcc3ab0] [c000000000e89e04] dev_attr_store+0x34/0x78 > [c00000000bcc3ad0] [c0000000007f8dd4] sysfs_kf_write+0x70/0xa4 > [c00000000bcc3af0] [c0000000007f7248] kernfs_fop_write_iter+0x1d0/0x2e0 > [c00000000bcc3b40] [c0000000006c9b08] vfs_write+0x27c/0x558 > [c00000000bcc3bf0] [c0000000006ca168] ksys_write+0x90/0x170 > [c00000000bcc3c40] [c000000000033248] system_call_exception+0xf8/0x290 > [c00000000bcc3e50] [c00000000000d05c] system_call_vectored_common+0x15c/0x2ec > > > A git bisect pointed this regression to be introduced via [1] that added > a mechanism to create device tree nodes for parent PCI bridges when a > PCI device is hot-plugged. > > The Oops is caused when `pci_stop_dev()` tries to remove a non-existing > device-tree node associated with the pci_dev that was earlier > hot-plugged and was attached under a pci-bridge. The PCI dev header > `dev->hdr_type` being 0, results a conditional check done with > `pci_is_bridge()` into false. Consequently, a call to > `of_pci_make_dev_node()` to create a device node is never made. When at > a later point in time, in the device node removal path, a memcpy is > attempted in `__of_changeset_entry_invert()`; since the device node was > never created, results in an Oops due to kernel read access to a bad > address. I'm sure this description is 100% correct, but it's at such a low level that it doesn't really help understand the underlying design problem. Will need an ack from Rob. > To fix this issue, the patch introduces a new flag OF_CREATE_WITH_CSET > to keep track of device nodes created via `of_pci_make_dev_node()` and > later attempt to destroy only such device nodes which have this flag > set. > > [1] commit 407d1a51921e ("PCI: Create device tree node for bridge") > > Fixes: 407d1a51921e ("PCI: Create device tree node for bridge") > Reported-by: Kowshik Jois B S > Signed-off-by: Lizhi Hou > Signed-off-by: Amit Machhiwal > --- > Changes since v2: > * Drop v2 changes and introduce a different approach from Lizhi discussed > over the v2 of this patch > * V2: https://lore.kernel.org/all/20240715080726.2496198-1-amachhiw@linux.ibm.com/ > Changes since v1: > * Included Lizhi's suggested changes on V1 > * Fixed below two warnings from Lizhi's changes and rearranged the cleanup > part a bit in `of_pci_make_dev_node` > drivers/pci/of.c:611:6: warning: no previous prototype for ‘of_pci_free_node’ [-Wmissing-prototypes] > 611 | void of_pci_free_node(struct device_node *np) > | ^~~~~~~~~~~~~~~~ > drivers/pci/of.c: In function ‘of_pci_make_dev_node’: > drivers/pci/of.c:696:1: warning: label ‘out_destroy_cset’ defined but not used [-Wunused-label] > 696 | out_destroy_cset: > | ^~~~~~~~~~~~~~~~ > * V1: https://lore.kernel.org/all/20240703141634.2974589-1-amachhiw@linux.ibm.com/ > > drivers/pci/of.c | 3 ++- > include/linux/of.h | 1 + > 2 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/of.c b/drivers/pci/of.c > index dacea3fc5128..bc455370143e 100644 > --- a/drivers/pci/of.c > +++ b/drivers/pci/of.c > @@ -653,7 +653,7 @@ void of_pci_remove_node(struct pci_dev *pdev) > struct device_node *np; > > np = pci_device_to_OF_node(pdev); > - if (!np || !of_node_check_flag(np, OF_DYNAMIC)) > + if (!np || !of_node_check_flag(np, OF_CREATE_WITH_CSET)) > return; > pdev->dev.of_node = NULL; of_pci_remove_node() goes on to call of_changeset_revert() and of_changeset_destroy(). of_pci_remove_node() has nothing PCI-specific in it. There are a few other callers of of_changeset_destroy(), but they don't look anything like of_pci_remove_node(). Seems like there should be some similarity across the callers, so it makes me a little nervous that there isn't. > @@ -712,6 +712,7 @@ void of_pci_make_dev_node(struct pci_dev *pdev) > if (ret) > goto out_free_node; > > + of_node_set_flag(np, OF_CREATE_WITH_CSET); > np->data = cset; > pdev->dev.of_node = np; > kfree(name); > diff --git a/include/linux/of.h b/include/linux/of.h > index 85b60ac9eec5..5faa5a1198c6 100644 > --- a/include/linux/of.h > +++ b/include/linux/of.h > @@ -153,6 +153,7 @@ extern struct device_node *of_stdout; > #define OF_POPULATED_BUS 4 /* platform bus created for children */ > #define OF_OVERLAY 5 /* allocated for an overlay */ > #define OF_OVERLAY_FREE_CSET 6 /* in overlay cset being freed */ > +#define OF_CREATE_WITH_CSET 7 /* Created by of_changeset_create_node */ Follow existing capitalization style.