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Message-ID: <f70e8e07-93e0-09bd-1d90-ee5458fb09f3@amd.com>
Date: Mon, 15 Jul 2024 13:35:58 -0700
From: Lizhi Hou <lizhi.hou@....com>
To: Bjorn Helgaas <helgaas@...nel.org>
CC: Amit Machhiwal <amachhiw@...ux.ibm.com>, <linux-pci@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
<linuxppc-dev@...ts.ozlabs.org>, <kvm-ppc@...r.kernel.org>, Bjorn Helgaas
<bhelgaas@...gle.com>, Rob Herring <robh@...nel.org>, Saravana Kannan
<saravanak@...gle.com>, Vaibhav Jain <vaibhav@...ux.ibm.com>, Nicholas Piggin
<npiggin@...il.com>, Michael Ellerman <mpe@...erman.id.au>, Vaidyanathan
Srinivasan <svaidy@...ux.ibm.com>, Kowshik Jois B S <kowsjois@...ux.ibm.com>,
Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH v2] PCI: Fix crash during pci_dev hot-unplug on pseries
KVM guest
On 7/15/24 10:23, Bjorn Helgaas wrote:
> On Mon, Jul 15, 2024 at 09:20:01AM -0700, Lizhi Hou wrote:
>> On 7/15/24 01:07, 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
>>> <snip>
>>> 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
>>> <snip>
>>>
>>> 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 <kowsjois@...ux.ibm.com>
>>> Signed-off-by: Lizhi Hou <lizhi.hou@....com>
>>> Signed-off-by: Amit Machhiwal <amachhiw@...ux.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/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(-)
>>>
>>> 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);
>> Please undo this change. It should only create the device node for bridges
>> and the pci endpoints listed in quirks for now.
> IIUC, you want Amit to post a v3 of this patch that omits this
> specific pci_bus_add_device() change?
Yes.
Lizhi
>
>>> 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,
>>>
>>> base-commit: 43db1e03c086ed20cc75808d3f45e780ec4ca26e
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