From 278294798ac9118412c9624a801d3f20f2279363 Mon Sep 17 00:00:00 2001 From: Ira Weiny Date: Mon, 26 Sep 2022 14:57:10 -0700 Subject: PCI: Allow drivers to request exclusive config regions PCI config space access from user space has traditionally been unrestricted with writes being an understood risk for device operation. Unfortunately, device breakage or odd behavior from config writes lacks indicators that can leave driver writers confused when evaluating failures. This is especially true with the new PCIe Data Object Exchange (DOE) mailbox protocol where backdoor shenanigans from user space through things such as vendor defined protocols may affect device operation without complete breakage. A prior proposal restricted read and writes completely.[1] Greg and Bjorn pointed out that proposal is flawed for a couple of reasons. First, lspci should always be allowed and should not interfere with any device operation. Second, setpci is a valuable tool that is sometimes necessary and it should not be completely restricted.[2] Finally methods exist for full lock of device access if required. Even though access should not be restricted it would be nice for driver writers to be able to flag critical parts of the config space such that interference from user space can be detected. Introduce pci_request_config_region_exclusive() to mark exclusive config regions. Such regions trigger a warning and kernel taint if accessed via user space. Create pci_warn_once() to restrict the user from spamming the log. [1] https://lore.kernel.org/all/161663543465.1867664.5674061943008380442.stgit@dwillia2-desk3.amr.corp.intel.com/ [2] https://lore.kernel.org/all/YF8NGeGv9vYcMfTV@kroah.com/ Cc: Bjorn Helgaas Cc: Greg Kroah-Hartman Reviewed-by: Jonathan Cameron Suggested-by: Dan Williams Signed-off-by: Ira Weiny Acked-by: Greg Kroah-Hartman Acked-by: Bjorn Helgaas Link: https://lore.kernel.org/r/20220926215711.2893286-2-ira.weiny@intel.com Signed-off-by: Dan Williams --- drivers/pci/pci-sysfs.c | 7 +++++++ drivers/pci/probe.c | 6 ++++++ include/linux/ioport.h | 2 ++ include/linux/pci.h | 17 +++++++++++++++++ kernel/resource.c | 13 ++++++++----- 5 files changed, 40 insertions(+), 5 deletions(-) diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 0a2eeb82cebd..6c250eb214e8 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -756,6 +756,13 @@ static ssize_t pci_write_config(struct file *filp, struct kobject *kobj, if (ret) return ret; + if (resource_is_exclusive(&dev->driver_exclusive_resource, off, + count)) { + pci_warn_once(dev, "%s: Unexpected write to kernel-exclusive config offset %llx", + current->comm, off); + add_taint(TAINT_USER, LOCKDEP_STILL_OK); + } + if (off > dev->cfg_size) return 0; if (off + count > dev->cfg_size) { diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index b66fa42c4b1f..2f4e88a44e8b 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -2307,6 +2307,12 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus) INIT_LIST_HEAD(&dev->bus_list); dev->dev.type = &pci_dev_type; dev->bus = pci_bus_get(bus); + dev->driver_exclusive_resource = (struct resource) { + .name = "PCI Exclusive", + .start = 0, + .end = -1, + }; + #ifdef CONFIG_PCI_MSI raw_spin_lock_init(&dev->msi_lock); #endif diff --git a/include/linux/ioport.h b/include/linux/ioport.h index 27642ca15d93..4ae3c541ea6f 100644 --- a/include/linux/ioport.h +++ b/include/linux/ioport.h @@ -318,6 +318,8 @@ extern void __devm_release_region(struct device *dev, struct resource *parent, resource_size_t start, resource_size_t n); extern int iomem_map_sanity_check(resource_size_t addr, unsigned long size); extern bool iomem_is_exclusive(u64 addr); +extern bool resource_is_exclusive(struct resource *resource, u64 addr, + resource_size_t size); extern int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages, diff --git a/include/linux/pci.h b/include/linux/pci.h index 2bda4a4e47e8..575849a100a3 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -409,6 +409,7 @@ struct pci_dev { */ unsigned int irq; struct resource resource[DEVICE_COUNT_RESOURCE]; /* I/O and memory regions + expansion ROMs */ + struct resource driver_exclusive_resource; /* driver exclusive resource ranges */ bool match_driver; /* Skip attaching driver */ @@ -1407,6 +1408,21 @@ int pci_request_selected_regions(struct pci_dev *, int, const char *); int pci_request_selected_regions_exclusive(struct pci_dev *, int, const char *); void pci_release_selected_regions(struct pci_dev *, int); +static inline __must_check struct resource * +pci_request_config_region_exclusive(struct pci_dev *pdev, unsigned int offset, + unsigned int len, const char *name) +{ + return __request_region(&pdev->driver_exclusive_resource, offset, len, + name, IORESOURCE_EXCLUSIVE); +} + +static inline void pci_release_config_region(struct pci_dev *pdev, + unsigned int offset, + unsigned int len) +{ + __release_region(&pdev->driver_exclusive_resource, offset, len); +} + /* drivers/pci/bus.c */ void pci_add_resource(struct list_head *resources, struct resource *res); void pci_add_resource_offset(struct list_head *resources, struct resource *res, @@ -2484,6 +2500,7 @@ void pci_uevent_ers(struct pci_dev *pdev, enum pci_ers_result err_type); #define pci_crit(pdev, fmt, arg...) dev_crit(&(pdev)->dev, fmt, ##arg) #define pci_err(pdev, fmt, arg...) dev_err(&(pdev)->dev, fmt, ##arg) #define pci_warn(pdev, fmt, arg...) dev_warn(&(pdev)->dev, fmt, ##arg) +#define pci_warn_once(pdev, fmt, arg...) dev_warn_once(&(pdev)->dev, fmt, ##arg) #define pci_notice(pdev, fmt, arg...) dev_notice(&(pdev)->dev, fmt, ##arg) #define pci_info(pdev, fmt, arg...) dev_info(&(pdev)->dev, fmt, ##arg) #define pci_dbg(pdev, fmt, arg...) dev_dbg(&(pdev)->dev, fmt, ##arg) diff --git a/kernel/resource.c b/kernel/resource.c index 4c5e80b92f2f..82ed54cd1f0d 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -1707,18 +1707,15 @@ static int strict_iomem_checks; * * Returns true if exclusive to the kernel, otherwise returns false. */ -bool iomem_is_exclusive(u64 addr) +bool resource_is_exclusive(struct resource *root, u64 addr, resource_size_t size) { const unsigned int exclusive_system_ram = IORESOURCE_SYSTEM_RAM | IORESOURCE_EXCLUSIVE; bool skip_children = false, err = false; - int size = PAGE_SIZE; struct resource *p; - addr = addr & PAGE_MASK; - read_lock(&resource_lock); - for_each_resource(&iomem_resource, p, skip_children) { + for_each_resource(root, p, skip_children) { if (p->start >= addr + size) break; if (p->end < addr) { @@ -1757,6 +1754,12 @@ bool iomem_is_exclusive(u64 addr) return err; } +bool iomem_is_exclusive(u64 addr) +{ + return resource_is_exclusive(&iomem_resource, addr & PAGE_MASK, + PAGE_SIZE); +} + struct resource_entry *resource_list_create_entry(struct resource *res, size_t extra_size) { -- cgit v1.2.3