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 2C8D718AF4; Fri, 5 Jul 2024 19:20:36 +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=1720207237; cv=none; b=NsmI3I1/q2Az1leaEyV8TjqAw0otld6k31Kc0FD33+L5l9yf0STLDQN0LLxDWeFE2b3ss1o5gGm5zIvkQ5qV51p8OpjFdWDILAdx+WdH+pCTj8z2OgpIHGJ4KpNBHa5+PXvuOlgFbXu/+bDTjBZZlfJF4x2VFbKqoh+ZyF7UCK4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720207237; c=relaxed/simple; bh=HchELO8nLBln8sfZVXM5+tcXKtpO4xsgC76A+YN3J8g=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=IBStLihpRUAhHvBeh5n0meSW/IwTuF+tVNoty1RAq/j+j/UpdWirytmfCTnGhAnM9ua0fQeY21QzUMPP3cwgnJO2me42D2CYLb8Crm9o059bwzs38VnojfE/xlBfWgYj3BjUxf6qE1qA0NxQsqBCbyfxODIUxf75NejRl6KLop8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kBwILHie; 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="kBwILHie" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6141BC116B1; Fri, 5 Jul 2024 19:20:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1720207236; bh=HchELO8nLBln8sfZVXM5+tcXKtpO4xsgC76A+YN3J8g=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=kBwILHieC1Z6CJbKtY8lqZJUEsArAzL7hXxABbptIQwOhgNlWFXh9w8DeirvYXyYC d/e80w4K5Dvyuiq7djURjha6yprVRBwnwpuepZYwjO8hHPM4Eky4Fw87WTZV84eHMP j0QhW0xQ3idturpI38gYhlFARaO67tsFjbB+/1NZdtNNA9MdhRNhsSLS7OI2G4YpCq M8rGgPPJ1aauE62olyF3L8DBMukj7fzZrNetCy92bKy21NAesRhcP9SBPDkJfsLuAR dbSAp5iZtsVPGzpSCf/kxV6fF3oF2gCaMSEPQxnppoB/Oknp5hhM8vAr2BoX8qsVDf 3KayVZCxp5rRQ== Date: Fri, 5 Jul 2024 14:20:34 -0500 From: Bjorn Helgaas To: Amit Machhiwal Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, Bjorn Helgaas , Rob Herring , Lizhi Hou , Vaibhav Jain , Nicholas Piggin , Michael Ellerman , Vaidyanathan Srinivasan , Kowshik Jois B S , Lukas Wunner Subject: Re: [PATCH] PCI: Fix crash during pci_dev hot-unplug on pseries KVM guest Message-ID: <20240705192034.GA73447@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=us-ascii Content-Disposition: inline In-Reply-To: <20240703141634.2974589-1-amachhiw@linux.ibm.com> [+cc Lukas, FYI] On Wed, Jul 03, 2024 at 07:46:34PM +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: > > 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 > 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. > > To fix this issue the patch updates `pci_stop_dev()` to ensure that a > call to `of_pci_remove_node()` is only made for pci-bridge devices. > > [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 > Tested-by: Kowshik Jois B S > Signed-off-by: Amit Machhiwal Thanks for the patch and testing! Would like a reviewed-by from Lizhi. > --- > drivers/pci/remove.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c > index d749ea8250d6..4e51c64af416 100644 > --- a/drivers/pci/remove.c > +++ b/drivers/pci/remove.c > @@ -22,7 +22,8 @@ static void pci_stop_dev(struct pci_dev *dev) > device_release_driver(&dev->dev); > pci_proc_detach_device(dev); > pci_remove_sysfs_dev_files(dev); > - of_pci_remove_node(dev); > + if (pci_is_bridge(dev)) > + of_pci_remove_node(dev); IIUC, this basically undoes the work that was done by of_pci_make_dev_node(). The call of of_pci_make_dev_node() from pci_bus_add_device() was added by 407d1a51921e and is conditional on pci_is_bridge(), so it makes sense to me that the remove needs a similar condition. > pci_dev_assign_added(dev, false); > } > > base-commit: e9d22f7a6655941fc8b2b942ed354ec780936b3e > -- > 2.45.2 >