Messages in this thread Patch in this message | | | From | ira.weiny@intel ... | Subject | [PATCH V8 32/44] memremap_pages: Add Kconfig for DEVMAP_ACCESS_PROTECTION | Date | Thu, 27 Jan 2022 09:54:53 -0800 |
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From: Ira Weiny <ira.weiny@intel.com>
The persistent memory (PMEM) driver uses the memremap_pages facility to provide 'struct page' metadata (vmemmap) for PMEM. Given that PMEM capacity maybe orders of magnitude higher capacity than System RAM it presents a large vulnerability surface to stray writes. Unlike stray writes to System RAM, which may result in a crash or other undesirable behavior, stray writes to PMEM additionally are more likely to result in permanent data loss. Reboot is not a remediation for PMEM corruption like it is for System RAM.
Given that PMEM access from the kernel is limited to a constrained set of locations (PMEM driver, Filesystem-DAX, and direct-I/O to a DAX page), it is amenable to supervisor pkey protection.
Not all systems with PMEM will want additional protections. Therefore, add a Kconfig option for the user to configure the additional devmap protections.
Only systems with supervisor protection keys (PKS) are able to support this new protection so depend on ARCH_HAS_SUPERVISOR_PKEYS. Furthermore, select ARCH_ENABLE_SUPERVISOR_PKEYS to ensure that the architecture support is enabled if PMEM is the only use case.
Only PMEM which is advertised to the memory subsystem needs this protection. Therefore, the feature depends on NVDIMM_PFN.
A default of (NVDIMM_PFN && ARCH_HAS_SUPERVISOR_PKEYS) was suggested but logically that is the same as saying default 'yes' because both NVDIMM_PFN and ARCH_HAS_SUPERVISOR_PKEYS are required. Therefore a default of 'yes' is used.
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
--- Changes for V8 Split this out from [PATCH V7 13/18] memremap_pages: Add access protection via supervisor Protection Keys (PKS) --- mm/Kconfig | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/mm/Kconfig b/mm/Kconfig index 46f2bb15aa4e..67e0264acf7d 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -776,6 +776,24 @@ config ZONE_DEVICE If FS_DAX is enabled, then say Y. +config DEVMAP_ACCESS_PROTECTION + bool "Access protection for memremap_pages()" + depends on NVDIMM_PFN + depends on ARCH_HAS_SUPERVISOR_PKEYS + select ARCH_ENABLE_SUPERVISOR_PKEYS + default y + + help + Enable extra protections on device memory. This protects against + unintended access to devices such as a stray writes. This feature is + particularly useful to protect against corruption of persistent + memory. + + This depends on architecture support of supervisor PKeys and has no + overhead if the architecture does not support them. + + If you have persistent memory say 'Y'. + config DEV_PAGEMAP_OPS bool -- 2.31.1
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