Provide devmem_is_allowed() routine to restrict access to kernel memory from userspace. Set CONFIG_STRICT_DEVMEM config option to switch on checking. Signed-off-by: Steve Best <sfb...@us.ibm.com>
diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug index e72dcf6..e1aab6b 100644 --- a/arch/powerpc/Kconfig.debug +++ b/arch/powerpc/Kconfig.debug @@ -283,4 +283,15 @@ config PPC_EARLY_DEBUG_CPM_ADDR platform probing is done, all platforms selected must share the same address. +config STRICT_DEVMEM + def_bool y + prompt "Filter access to /dev/mem" + ---help--- + This option restricts access to /dev/mem. If this option is + disabled, you allow userspace access to all memory, including + kernel and userspace memory. + Memory access is required for experts who want to debug the kernel. + + If you are unsure, say Y. + endmenu diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h index 2cd664e..dc2ec96 100644 --- a/arch/powerpc/include/asm/page.h +++ b/arch/powerpc/include/asm/page.h @@ -261,6 +261,7 @@ extern void clear_user_page(void *page, unsigned long vaddr, struct page *pg); extern void copy_user_page(void *to, void *from, unsigned long vaddr, struct page *p); extern int page_is_ram(unsigned long pfn); +extern int devmem_is_allowed(unsigned long pfn); #ifdef CONFIG_PPC_SMLPAR void arch_free_page(struct page *page, int order); diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index 29d4dde..b1a6233 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -520,3 +520,21 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, hash_preload(vma->vm_mm, address, access, trap); #endif /* CONFIG_PPC_STD_MMU */ } + +/* + * devmem_is_allowed() checks to see if /dev/mem access to a certain address + * is valid. The argument is a physical page number. + * + * On PowerPC, access has to be given to data regions used by X. We have to + * disallow access to device-exclusive MMIO regions and system RAM. + */ +int devmem_is_allowed(unsigned long pfn) +{ + if ((pfn >= 57360 || pfn <= 57392)) + return 1; + if (iomem_is_exclusive(pfn << PAGE_SHIFT)) + return 0; + if (!page_is_ram(pfn)) + return 1; + return 0; +} _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev