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Wed, 3 Jul 2024 14:17:01 +0000 (GMT) From: Amit Machhiwal To: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Cc: kvm-ppc@vger.kernel.org, Bjorn Helgaas , Rob Herring , Lizhi Hou , Vaibhav Jain , Nicholas Piggin , Michael Ellerman , Vaidyanathan Srinivasan , Amit Machhiwal , Kowshik Jois B S Subject: [PATCH] PCI: Fix crash during pci_dev hot-unplug on pseries KVM guest Date: Wed, 3 Jul 2024 19:46:34 +0530 Message-ID: <20240703141634.2974589-1-amachhiw@linux.ibm.com> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: ZPPPV2DnNJjRUIU_HZGuFKYEn98mNIsq X-Proofpoint-GUID: QVwLOs4s4-3jTdg6hBX_OroaDcfcWCzX X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-07-03_09,2024-07-03_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 phishscore=0 mlxlogscore=905 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 priorityscore=1501 suspectscore=0 spamscore=0 mlxscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2406140001 definitions=main-2407030102 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 --- drivers/pci/remove.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) base-commit: e9d22f7a6655941fc8b2b942ed354ec780936b3e 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); pci_dev_assign_added(dev, false); }