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Mon, 15 Jul 2024 08:07:40 +0000 (GMT) From: Amit Machhiwal To: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, Bjorn Helgaas , Rob Herring , Lizhi Hou , Saravana Kannan , Vaibhav Jain , Nicholas Piggin , Michael Ellerman , Vaidyanathan Srinivasan , Amit Machhiwal , Kowshik Jois B S , Lukas Wunner Subject: [PATCH v2] PCI: Fix crash during pci_dev hot-unplug on pseries KVM guest Date: Mon, 15 Jul 2024 13:37:03 +0530 Message-ID: <20240715080726.2496198-1-amachhiw@linux.ibm.com> X-Mailer: git-send-email 2.45.2 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: aIL3wnqLkoZ_8k-83EyKvYgU9teBT1QM X-Proofpoint-ORIG-GUID: FOTFMXAAN-i3QXDqW9hYcKMV5nnOykP6 X-Proofpoint-UnRewURL: 0 URL was un-rewritten Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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=2024-07-15_03,2024-07-11_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 priorityscore=1501 suspectscore=0 phishscore=0 adultscore=0 clxscore=1011 lowpriorityscore=0 mlxlogscore=865 mlxscore=0 bulkscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2406140001 definitions=main-2407150061 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 `of_changeset_create_node()` to allocate a new node only when the device node doesn't exist and init it in case it does already. Also, introduce `of_pci_free_node()` to be called to only revert and destroy the changeset device node that was created via a call to `of_changeset_create_node()`. [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 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/of/dynamic.c | 16 ++++++++++++---- drivers/of/unittest.c | 2 +- drivers/pci/bus.c | 3 +-- drivers/pci/of.c | 39 ++++++++++++++++++++++++++------------- drivers/pci/pci.h | 2 ++ include/linux/of.h | 1 + 6 files changed, 43 insertions(+), 20 deletions(-) base-commit: 43db1e03c086ed20cc75808d3f45e780ec4ca26e diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c index dda6092e6d3a..9bba5e82a384 100644 --- a/drivers/of/dynamic.c +++ b/drivers/of/dynamic.c @@ -492,21 +492,29 @@ struct device_node *__of_node_dup(const struct device_node *np, * a given changeset. * * @ocs: Pointer to changeset + * @np: Pointer to device node. If null, allocate a new node. If not, init an + * existing one. * @parent: Pointer to parent device node * @full_name: Node full name * * Return: Pointer to the created device node or NULL in case of an error. */ struct device_node *of_changeset_create_node(struct of_changeset *ocs, + struct device_node *np, struct device_node *parent, const char *full_name) { - struct device_node *np; int ret; - np = __of_node_dup(NULL, full_name); - if (!np) - return NULL; + if (!np) { + np = __of_node_dup(NULL, full_name); + if (!np) + return NULL; + } else { + of_node_set_flag(np, OF_DYNAMIC); + of_node_set_flag(np, OF_DETACHED); + } + np->parent = parent; ret = of_changeset_attach_node(ocs, np); diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c index 445ad13dab98..b1bcc9ed40a6 100644 --- a/drivers/of/unittest.c +++ b/drivers/of/unittest.c @@ -871,7 +871,7 @@ static void __init of_unittest_changeset(void) unittest(!of_changeset_add_property(&chgset, parent, ppadd), "fail add prop prop-add\n"); unittest(!of_changeset_update_property(&chgset, parent, ppupdate), "fail update prop\n"); unittest(!of_changeset_remove_property(&chgset, parent, ppremove), "fail remove prop\n"); - n22 = of_changeset_create_node(&chgset, n2, "n22"); + n22 = of_changeset_create_node(&chgset, NULL, n2, "n22"); unittest(n22, "fail create n22\n"); unittest(!of_changeset_add_prop_string(&chgset, n22, "prop-str", "abcd"), "fail add prop prop-str"); diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c index 826b5016a101..d7ca20cb146a 100644 --- a/drivers/pci/bus.c +++ b/drivers/pci/bus.c @@ -342,8 +342,7 @@ void pci_bus_add_device(struct pci_dev *dev) */ pcibios_bus_add_device(dev); pci_fixup_device(pci_fixup_final, dev); - if (pci_is_bridge(dev)) - of_pci_make_dev_node(dev); + of_pci_make_dev_node(dev); pci_create_sysfs_dev_files(dev); pci_proc_attach_device(dev); pci_bridge_d3_update(dev); diff --git a/drivers/pci/of.c b/drivers/pci/of.c index 51e3dd0ea5ab..883bf15211a5 100644 --- a/drivers/pci/of.c +++ b/drivers/pci/of.c @@ -608,18 +608,28 @@ int devm_of_pci_bridge_init(struct device *dev, struct pci_host_bridge *bridge) #ifdef CONFIG_PCI_DYNAMIC_OF_NODES +void of_pci_free_node(struct device_node *np) +{ + struct of_changeset *cset; + + cset = (struct of_changeset *)(np + 1); + + np->data = NULL; + of_changeset_revert(cset); + of_changeset_destroy(cset); + of_node_put(np); +} + 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 || np->data != of_pci_free_node) return; pdev->dev.of_node = NULL; - of_changeset_revert(np->data); - of_changeset_destroy(np->data); - of_node_put(np); + of_pci_free_node(np); } void of_pci_make_dev_node(struct pci_dev *pdev) @@ -655,14 +665,18 @@ void of_pci_make_dev_node(struct pci_dev *pdev) if (!name) return; - cset = kmalloc(sizeof(*cset), GFP_KERNEL); - if (!cset) + np = kzalloc(sizeof(*np) + sizeof(*cset), GFP_KERNEL); + if (!np) goto out_free_name; + np->full_name = name; + of_node_init(np); + + cset = (struct of_changeset *)(np + 1); of_changeset_init(cset); - np = of_changeset_create_node(cset, ppnode, name); + np = of_changeset_create_node(cset, np, ppnode, NULL); if (!np) - goto out_destroy_cset; + goto out_free_node; ret = of_pci_add_properties(pdev, cset, np); if (ret) @@ -670,19 +684,18 @@ void of_pci_make_dev_node(struct pci_dev *pdev) ret = of_changeset_apply(cset); if (ret) - goto out_free_node; + goto out_destroy_cset; - np->data = cset; + np->data = of_pci_free_node; pdev->dev.of_node = np; - kfree(name); return; -out_free_node: - of_node_put(np); out_destroy_cset: of_changeset_destroy(cset); kfree(cset); +out_free_node: + of_node_put(np); out_free_name: kfree(name); } diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index fd44565c4756..7b1a455306b8 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -702,11 +702,13 @@ struct of_changeset; #ifdef CONFIG_PCI_DYNAMIC_OF_NODES void of_pci_make_dev_node(struct pci_dev *pdev); +void of_pci_free_node(struct device_node *np); void of_pci_remove_node(struct pci_dev *pdev); int of_pci_add_properties(struct pci_dev *pdev, struct of_changeset *ocs, struct device_node *np); #else static inline void of_pci_make_dev_node(struct pci_dev *pdev) { } +static inline void of_pci_free_node(struct device_node *np) { } static inline void of_pci_remove_node(struct pci_dev *pdev) { } #endif diff --git a/include/linux/of.h b/include/linux/of.h index a0bedd038a05..f774459d0d84 100644 --- a/include/linux/of.h +++ b/include/linux/of.h @@ -1631,6 +1631,7 @@ static inline int of_changeset_update_property(struct of_changeset *ocs, } struct device_node *of_changeset_create_node(struct of_changeset *ocs, + struct device_node *np, struct device_node *parent, const char *full_name); int of_changeset_add_prop_string(struct of_changeset *ocs,