diff options
| author | sukadev@linux.vnet.ibm.com <sukadev@linux.vnet.ibm.com> | 2011-08-30 09:19:17 +0000 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2011-11-28 11:42:08 +1100 |
| commit | 1d54cf2b973a6265789b382b7d305771321b9b57 (patch) | |
| tree | 8103c4c2accf96fd40cb1fb32ee9797aa97d17ed /arch/powerpc | |
| parent | 56368797d6c2d093bb0e7a7e5fe7b267274b6c58 (diff) | |
powerpc: Implement CONFIG_STRICT_DEVMEM
As described in the help text in the patch, this token restricts general
access to /dev/mem as a way of increasing the security. Specifically, access
to exclusive IOMEM and kernel RAM is denied unless CONFIG_STRICT_DEVMEM is
set to 'n'.
Implement the 'devmem_is_allowed()' interface for Powerpc. It will be
called from range_is_allowed() when userpsace attempts to access /dev/mem.
This patch is based on an earlier patch from Steve Best and with input from
Paul Mackerras and Scott Wood.
[BenH] Fixed a typo or two and removed the generic change which should
be submitted as a separate patch
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/Kconfig.debug | 12 | ||||
| -rw-r--r-- | arch/powerpc/include/asm/page.h | 1 | ||||
| -rw-r--r-- | arch/powerpc/mm/mem.c | 18 |
3 files changed, 31 insertions, 0 deletions
diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug index 1b8a9c905cf7..4ccb2a009f74 100644 --- a/arch/powerpc/Kconfig.debug +++ b/arch/powerpc/Kconfig.debug @@ -336,4 +336,16 @@ 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. Accidental memory access is likely + to be disastrous. + 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 dd9c4fd038e0..9d7485c7e6f8 100644 --- a/arch/powerpc/include/asm/page.h +++ b/arch/powerpc/include/asm/page.h @@ -290,6 +290,7 @@ 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 2dd6bdd31fe1..22563b9664c3 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -585,3 +585,21 @@ static int add_system_ram_resources(void) return 0; } subsys_initcall(add_system_ram_resources); + +#ifdef CONFIG_STRICT_DEVMEM +/* + * devmem_is_allowed(): check to see if /dev/mem access to a certain address + * is valid. The argument is a physical page number. + * + * Access has to be given to non-kernel-ram areas as well, these contain the + * PCI mmio resources as well as potential bios/acpi data regions. + */ +int devmem_is_allowed(unsigned long pfn) +{ + if (iomem_is_exclusive(pfn << PAGE_SHIFT)) + return 0; + if (!page_is_ram(pfn)) + return 1; + return 0; +} +#endif /* CONFIG_STRICT_DEVMEM */ |