user/sven/linux.git/kernel/resource.c, branch v6.1.124

resource: fix region_intersects() vs add_memory_driver_managed()

2024-10-17T13:21:55Z

commit b4afe4183ec77f230851ea139d91e5cf2644c68b upstream. On a system with CXL memory, the resource tree (/proc/iomem) related to CXL memory may look like something as follows. 490000000-50fffffff : CXL Window 0 490000000-50fffffff : region0 490000000-50fffffff : dax0.0 490000000-50fffffff : System RAM (kmem) Because drivers/dax/kmem.c calls add_memory_driver_managed() during onlining CXL memory, which makes "System RAM (kmem)" a descendant of "CXL Window X". This confuses region_intersects(), which expects all "System RAM" resources to be at the top level of iomem_resource. This can lead to bugs. For example, when the following command line is executed to write some memory in CXL memory range via /dev/mem, $ dd if=data of=/dev/mem bs=$((1 << 10)) seek=$((0x490000000 >> 10)) count=1 dd: error writing '/dev/mem': Bad address 1+0 records in 0+0 records out 0 bytes copied, 0.0283507 s, 0.0 kB/s the command fails as expected. However, the error code is wrong. It should be "Operation not permitted" instead of "Bad address". More seriously, the /dev/mem permission checking in devmem_is_allowed() passes incorrectly. Although the accessing is prevented later because ioremap() isn't allowed to map system RAM, it is a potential security issue. During command executing, the following warning is reported in the kernel log for calling ioremap() on system RAM. ioremap on RAM at 0x0000000490000000 - 0x0000000490000fff WARNING: CPU: 2 PID: 416 at arch/x86/mm/ioremap.c:216 __ioremap_caller.constprop.0+0x131/0x35d Call Trace: memremap+0xcb/0x184 xlate_dev_mem_ptr+0x25/0x2f write_mem+0x94/0xfb vfs_write+0x128/0x26d ksys_write+0xac/0xfe do_syscall_64+0x9a/0xfd entry_SYSCALL_64_after_hwframe+0x4b/0x53 The details of command execution process are as follows. In the above resource tree, "System RAM" is a descendant of "CXL Window 0" instead of a top level resource. So, region_intersects() will report no System RAM resources in the CXL memory region incorrectly, because it only checks the top level resources. Consequently, devmem_is_allowed() will return 1 (allow access via /dev/mem) for CXL memory region incorrectly. Fortunately, ioremap() doesn't allow to map System RAM and reject the access. So, region_intersects() needs to be fixed to work correctly with the resource tree with "System RAM" not at top level as above. To fix it, if we found a unmatched resource in the top level, we will continue to search matched resources in its descendant resources. So, we will not miss any matched resources in resource tree anymore. In the new implementation, an example resource tree |------------- "CXL Window 0" ------------| |-- "System RAM" --| will behave similar as the following fake resource tree for region_intersects(, IORESOURCE_SYSTEM_RAM, ), |-- "System RAM" --||-- "CXL Window 0a" --| Where "CXL Window 0a" is part of the original "CXL Window 0" that isn't covered by "System RAM". Link: https://lkml.kernel.org/r/20240906030713.204292-2-ying.huang@intel.com Fixes: c221c0b0308f ("device-dax: "Hotplug" persistent memory for use like normal RAM") Signed-off-by: "Huang, Ying" Cc: Dan Williams Cc: David Hildenbrand Cc: Davidlohr Bueso Cc: Jonathan Cameron Cc: Dave Jiang Cc: Alison Schofield Cc: Vishal Verma Cc: Ira Weiny Cc: Alistair Popple Cc: Andy Shevchenko Cc: Bjorn Helgaas Cc: Baoquan He Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

x86/kaslr: Expose and use the end of the physical memory address space

2024-09-12T09:10:17Z

commit ea72ce5da22806d5713f3ffb39a6d5ae73841f93 upstream. iounmap() on x86 occasionally fails to unmap because the provided valid ioremap address is not below high_memory. It turned out that this happens due to KASLR. KASLR uses the full address space between PAGE_OFFSET and vaddr_end to randomize the starting points of the direct map, vmalloc and vmemmap regions. It thereby limits the size of the direct map by using the installed memory size plus an extra configurable margin for hot-plug memory. This limitation is done to gain more randomization space because otherwise only the holes between the direct map, vmalloc, vmemmap and vaddr_end would be usable for randomizing. The limited direct map size is not exposed to the rest of the kernel, so the memory hot-plug and resource management related code paths still operate under the assumption that the available address space can be determined with MAX_PHYSMEM_BITS. request_free_mem_region() allocates from (1 << MAX_PHYSMEM_BITS) - 1 downwards. That means the first allocation happens past the end of the direct map and if unlucky this address is in the vmalloc space, which causes high_memory to become greater than VMALLOC_START and consequently causes iounmap() to fail for valid ioremap addresses. MAX_PHYSMEM_BITS cannot be changed for that because the randomization does not align with address bit boundaries and there are other places which actually require to know the maximum number of address bits. All remaining usage sites of MAX_PHYSMEM_BITS have been analyzed and found to be correct. Cure this by exposing the end of the direct map via PHYSMEM_END and use that for the memory hot-plug and resource management related places instead of relying on MAX_PHYSMEM_BITS. In the KASLR case PHYSMEM_END maps to a variable which is initialized by the KASLR initialization and otherwise it is based on MAX_PHYSMEM_BITS as before. To prevent future hickups add a check into add_pages() to catch callers trying to add memory above PHYSMEM_END. Fixes: 0483e1fa6e09 ("x86/mm: Implement ASLR for kernel memory regions") Reported-by: Max Ramanouski Reported-by: Alistair Popple Signed-off-by: Thomas Gleixner Tested-By: Max Ramanouski Tested-by: Alistair Popple Reviewed-by: Dan Williams Reviewed-by: Alistair Popple Reviewed-by: Kees Cook Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/87ed6soy3z.ffs@tglx Signed-off-by: Greg Kroah-Hartman

PCI: Allow drivers to request exclusive config regions

2023-09-13T07:42:46Z

[ Upstream commit 278294798ac9118412c9624a801d3f20f2279363 ] 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 Stable-dep-of: 5e70d0acf082 ("PCI: Add locking to RMW PCI Express Capability Register accessors") Signed-off-by: Sasha Levin

dax/kmem: Fix leak of memory-hotplug resources

2023-03-10T08:34:25Z

commit e686c32590f40bffc45f105c04c836ffad3e531a upstream. While experimenting with CXL region removal the following corruption of /proc/iomem appeared. Before: f010000000-f04fffffff : CXL Window 0 f010000000-f02fffffff : region4 f010000000-f02fffffff : dax4.0 f010000000-f02fffffff : System RAM (kmem) After (modprobe -r cxl_test): f010000000-f02fffffff : **redacted binary garbage** f010000000-f02fffffff : System RAM (kmem) ...and testing further the same is visible with persistent memory assigned to kmem: Before: 480000000-243fffffff : Persistent Memory 480000000-57e1fffff : namespace3.0 580000000-243fffffff : dax3.0 580000000-243fffffff : System RAM (kmem) After (ndctl disable-region all): 480000000-243fffffff : Persistent Memory 580000000-243fffffff : ***redacted binary garbage*** 580000000-243fffffff : System RAM (kmem) The corrupted data is from a use-after-free of the "dax4.0" and "dax3.0" resources, and it also shows that the "System RAM (kmem)" resource is not being removed. The bug does not appear after "modprobe -r kmem", it requires the parent of "dax4.0" and "dax3.0" to be removed which re-parents the leaked "System RAM (kmem)" instances. Those in turn reference the freed resource as a parent. First up for the fix is release_mem_region_adjustable() needs to reliably delete the resource inserted by add_memory_driver_managed(). That is thwarted by a check for IORESOURCE_SYSRAM that predates the dax/kmem driver, from commit: 65c78784135f ("kernel, resource: check for IORESOURCE_SYSRAM in release_mem_region_adjustable") That appears to be working around the behavior of HMM's "MEMORY_DEVICE_PUBLIC" facility that has since been deleted. With that check removed the "System RAM (kmem)" resource gets removed, but corruption still occurs occasionally because the "dax" resource is not reliably removed. The dax range information is freed before the device is unregistered, so the driver can not reliably recall (another use after free) what it is meant to release. Lastly if that use after free got lucky, the driver was covering up the leak of "System RAM (kmem)" due to its use of release_resource() which detaches, but does not free, child resources. The switch to remove_resource() forces remove_memory() to be responsible for the deletion of the resource added by add_memory_driver_managed(). Fixes: c2f3011ee697 ("device-dax: add an allocation interface for device-dax instances") Cc: Cc: Oscar Salvador Cc: David Hildenbrand Cc: Pavel Tatashin Reviewed-by: Vishal Verma Reviewed-by: Pasha Tatashin Reviewed-by: Dave Jiang Link: https://lore.kernel.org/r/167653656244.3147810.5705900882794040229.stgit@dwillia2-xfh.jf.intel.com Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman

resource: Introduce alloc_free_mem_region()

2022-07-22T00:19:25Z

The core of devm_request_free_mem_region() is a helper that searches for free space in iomem_resource and performs __request_region_locked() on the result of that search. The policy choices of the implementation conform to what CONFIG_DEVICE_PRIVATE users want which is memory that is immediately marked busy, and a preference to search for the first-fit free range in descending order from the top of the physical address space. CXL has a need for a similar allocator, but with the following tweaks: 1/ Search for free space in ascending order 2/ Search for free space relative to a given CXL window 3/ 'insert' rather than 'request' the new resource given downstream drivers from the CXL Region driver (like the pmem or dax drivers) are responsible for request_mem_region() when they activate the memory range. Rework __request_free_mem_region() into get_free_mem_region() which takes a set of GFR_* (Get Free Region) flags to control the allocation policy (ascending vs descending), and "busy" policy (insert_resource() vs request_region()). As part of the consolidation of the legacy GFR_REQUEST_REGION case with the new default of just inserting a new resource into the free space some minor cleanups like not checking for NULL before calling devres_free() (which does its own check) is included. Suggested-by: Jason Gunthorpe Link: https://lore.kernel.org/linux-cxl/20220420143406.GY2120790@nvidia.com/ Cc: Matthew Wilcox Cc: Christoph Hellwig Reviewed-by: Jonathan Cameron Link: https://lore.kernel.org/r/165784333333.1758207.13703329337805274043.stgit@dwillia2-xfh.jf.intel.com Signed-off-by: Dan Williams

cxl/acpi: Track CXL resources in iomem_resource

2022-07-21T15:40:01Z

Recall that CXL capable address ranges, on ACPI platforms, are published in the CEDT.CFMWS (CXL Early Discovery Table: CXL Fixed Memory Window Structures). These windows represent both the actively mapped capacity and the potential address space that can be dynamically assigned to a new CXL decode configuration (region / interleave-set). CXL endpoints like DDR DIMMs can be mapped at any physical address including 0 and legacy ranges. There is an expectation and requirement that the /proc/iomem interface and the iomem_resource tree in the kernel reflect the full set of platform address ranges. I.e. that every address range that platform firmware and bus drivers enumerate be reflected as an iomem_resource entry. The hard requirement to do this for CXL arises from the fact that facilities like CONFIG_DEVICE_PRIVATE expect to be able to treat empty iomem_resource ranges as free for software to use as proxy address space. Without CXL publishing its potential address ranges in iomem_resource, the CONFIG_DEVICE_PRIVATE mechanism may inadvertently steal capacity reserved for runtime provisioning of new CXL regions. So, iomem_resource needs to know about both active and potential CXL resource ranges. The active CXL resources might already be reflected in iomem_resource as "System RAM". insert_resource_expand_to_fit() handles re-parenting "System RAM" underneath a CXL window. The "_expand_to_fit()" behavior handles cases where a CXL window is not a strict superset of an existing entry in the iomem_resource tree. The "_expand_to_fit()" behavior is acceptable from the perspective of resource allocation. The expansion happens because a conflicting resource range is already populated, which means the resource boundary expansion does not result in any additional free CXL address space being made available. CXL address space allocation is always bounded by the orginal unexpanded address range. However, the potential for expansion does mean that something like walk_iomem_res_desc(IORES_DESC_CXL...) can only return fuzzy answers on corner case platforms that cause the resource tree to expand a CXL window resource over a range that is not decoded by CXL. This would be an odd platform configuration, but if it becomes a problem in practice the CXL subsytem could just publish an API that returns definitive answers. Cc: Andrew Morton Cc: David Hildenbrand Cc: Jason Gunthorpe Cc: Tony Luck Cc: Christoph Hellwig Reviewed-by: Jonathan Cameron Acked-by: Greg Kroah-Hartman Link: https://lore.kernel.org/r/165784325943.1758207.5310344844375305118.stgit@dwillia2-xfh.jf.intel.com Signed-off-by: Dan Williams

kernel/resource: fix kfree() of bootmem memory again

2022-03-24T02:00:35Z

Since commit ebff7d8f270d ("mem hotunplug: fix kfree() of bootmem memory"), we could get a resource allocated during boot via alloc_resource(). And it's required to release the resource using free_resource(). Howerver, many people use kfree directly which will result in kernel BUG. In order to fix this without fixing every call site, just leak a couple of bytes in such corner case. Link: https://lkml.kernel.org/r/20220217083619.19305-1-linmiaohe@huawei.com Fixes: ebff7d8f270d ("mem hotunplug: fix kfree() of bootmem memory") Signed-off-by: Miaohe Lin Suggested-by: David Hildenbrand Cc: Dan Williams Cc: Alistair Popple Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

proc: remove PDE_DATA() completely

2022-01-22T06:33:37Z

Remove PDE_DATA() completely and replace it with pde_data(). [akpm@linux-foundation.org: fix naming clash in drivers/nubus/proc.c] [akpm@linux-foundation.org: now fix it properly] Link: https://lkml.kernel.org/r/20211124081956.87711-2-songmuchun@bytedance.com Signed-off-by: Muchun Song Acked-by: Christian Brauner Cc: Alexey Dobriyan Cc: Alexey Gladkov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/resource: disallow access to exclusive system RAM regions

2021-11-09T18:02:52Z

virtio-mem dynamically exposes memory inside a device memory region as system RAM to Linux, coordinating with the hypervisor which parts are actually "plugged" and consequently usable/accessible. On the one hand, the virtio-mem driver adds/removes whole memory blocks, creating/removing busy IORESOURCE_SYSTEM_RAM resources, on the other hand, it logically (un)plugs memory inside added memory blocks, dynamically either exposing them to the buddy or hiding them from the buddy and marking them PG_offline. In contrast to physical devices, like a DIMM, the virtio-mem driver is required to actually make use of any of the device-provided memory, because it performs the handshake with the hypervisor. virtio-mem memory cannot simply be access via /dev/mem without a driver. There is no safe way to: a) Access plugged memory blocks via /dev/mem, as they might contain unplugged holes or might get silently unplugged by the virtio-mem driver and consequently turned inaccessible. b) Access unplugged memory blocks via /dev/mem because the virtio-mem driver is required to make them actually accessible first. The virtio-spec states that unplugged memory blocks MUST NOT be written, and only selected unplugged memory blocks MAY be read. We want to make sure, this is the case in sane environments -- where the virtio-mem driver was loaded. We want to make sure that in a sane environment, nobody "accidentially" accesses unplugged memory inside the device managed region. For example, a user might spot a memory region in /proc/iomem and try accessing it via /dev/mem via gdb or dumping it via something else. By the time the mmap() happens, the memory might already have been removed by the virtio-mem driver silently: the mmap() would succeeed and user space might accidentially access unplugged memory. So once the driver was loaded and detected the device along the device-managed region, we just want to disallow any access via /dev/mem to it. In an ideal world, we would mark the whole region as busy ("owned by a driver") and exclude it; however, that would be wrong, as we don't really have actual system RAM at these ranges added to Linux ("busy system RAM"). Instead, we want to mark such ranges as "not actual busy system RAM but still soft-reserved and prepared by a driver for future use." Let's teach iomem_is_exclusive() to reject access to any range with "IORESOURCE_SYSTEM_RAM | IORESOURCE_EXCLUSIVE", even if not busy and even if "iomem=relaxed" is set. Introduce EXCLUSIVE_SYSTEM_RAM to make it easier for applicable drivers to depend on this setting in their Kconfig. For now, there are no applicable ranges and we'll modify virtio-mem next to properly set IORESOURCE_EXCLUSIVE on the parent resource container it creates to contain all actual busy system RAM added via add_memory_driver_managed(). Link: https://lkml.kernel.org/r/20210920142856.17758-3-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Dan Williams Cc: Andy Shevchenko Cc: Arnd Bergmann Cc: Greg Kroah-Hartman Cc: Hanjun Guo Cc: Jason Wang Cc: "Michael S. Tsirkin" Cc: "Rafael J. Wysocki" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/resource: clean up and optimize iomem_is_exclusive()

2021-11-09T18:02:52Z

Patch series "virtio-mem: disallow mapping virtio-mem memory via /dev/mem", v5. Let's add the basic infrastructure to exclude some physical memory regions marked as "IORESOURCE_SYSTEM_RAM" completely from /dev/mem access, even though they are not marked IORESOURCE_BUSY and even though "iomem=relaxed" is set. Resource IORESOURCE_EXCLUSIVE for that purpose instead of adding new flags to express something similar to "soft-busy" or "not busy yet, but already prepared by a driver and not to be mapped by user space". Use it for virtio-mem, to disallow mapping any virtio-mem memory via /dev/mem to user space after the virtio-mem driver was loaded. This patch (of 3): We end up traversing subtrees of ranges we are not interested in; let's optimize this case, skipping such subtrees, cleaning up the function a bit. For example, in the following configuration (/proc/iomem): 00000000-00000fff : Reserved 00001000-00057fff : System RAM 00058000-00058fff : Reserved 00059000-0009cfff : System RAM 0009d000-000fffff : Reserved 000a0000-000bffff : PCI Bus 0000:00 000c0000-000c3fff : PCI Bus 0000:00 000c4000-000c7fff : PCI Bus 0000:00 000c8000-000cbfff : PCI Bus 0000:00 000cc000-000cffff : PCI Bus 0000:00 000d0000-000d3fff : PCI Bus 0000:00 000d4000-000d7fff : PCI Bus 0000:00 000d8000-000dbfff : PCI Bus 0000:00 000dc000-000dffff : PCI Bus 0000:00 000e0000-000e3fff : PCI Bus 0000:00 000e4000-000e7fff : PCI Bus 0000:00 000e8000-000ebfff : PCI Bus 0000:00 000ec000-000effff : PCI Bus 0000:00 000f0000-000fffff : PCI Bus 0000:00 000f0000-000fffff : System ROM 00100000-3fffffff : System RAM 40000000-403fffff : Reserved 40000000-403fffff : pnp 00:00 40400000-80a79fff : System RAM ... We don't have to look at any children of "0009d000-000fffff : Reserved" if we can just skip these 15 items directly because the parent range is not of interest. Link: https://lkml.kernel.org/r/20210920142856.17758-1-david@redhat.com Link: https://lkml.kernel.org/r/20210920142856.17758-2-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Dan Williams Cc: Arnd Bergmann Cc: Greg Kroah-Hartman Cc: "Michael S. Tsirkin" Cc: Jason Wang Cc: "Rafael J. Wysocki" Cc: Hanjun Guo Cc: Andy Shevchenko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds