On 14-07-28 10:58 PM, Yang Shi wrote: > From: Kees Cook <[email protected]> > > commit e2b32e6785138d92d2a40e0d0473575c8c7310a2 upstream
Unless I missed it, it would be nice if these 3 patches had a 0/3 that had some context about what they are fixing and why they are selected for cherry pick. See here for an example: http://article.gmane.org/gmane.comp.handhelds.openembedded.core/53772 Thanks, Paul. -- > > Randomize the load address of modules in the kernel to make kASLR > effective for modules. Modules can only be loaded within a particular > range of virtual address space. This patch adds 10 bits of entropy to > the load address by adding 1-1024 * PAGE_SIZE to the beginning range > where modules are loaded. > > The single base offset was chosen because randomizing each module > load ends up wasting/fragmenting memory too much. Prior approaches to > minimizing fragmentation while doing randomization tend to result in > worse entropy than just doing a single base address offset. > > Example kASLR boot without this change, with a single module loaded: > ---[ Modules ]--- > 0xffffffffc0000000-0xffffffffc0001000 4K ro GLB x pte > 0xffffffffc0001000-0xffffffffc0002000 4K ro GLB NX pte > 0xffffffffc0002000-0xffffffffc0004000 8K RW GLB NX pte > 0xffffffffc0004000-0xffffffffc0200000 2032K pte > 0xffffffffc0200000-0xffffffffff000000 1006M pmd > ---[ End Modules ]--- > > Example kASLR boot after this change, same module loaded: > ---[ Modules ]--- > 0xffffffffc0000000-0xffffffffc0200000 2M pmd > 0xffffffffc0200000-0xffffffffc03bf000 1788K pte > 0xffffffffc03bf000-0xffffffffc03c0000 4K ro GLB x pte > 0xffffffffc03c0000-0xffffffffc03c1000 4K ro GLB NX pte > 0xffffffffc03c1000-0xffffffffc03c3000 8K RW GLB NX pte > 0xffffffffc03c3000-0xffffffffc0400000 244K pte > 0xffffffffc0400000-0xffffffffff000000 1004M pmd > ---[ End Modules ]--- > > Signed-off-by: Andy Honig <[email protected]> > Link: http://lkml.kernel.org/r/[email protected] > Signed-off-by: Kees Cook <[email protected]> > Signed-off-by: H. Peter Anvin <[email protected]> > Signed-off-by: Yang Shi <[email protected]> > --- > Documentation/kernel-parameters.txt | 4 ++-- > arch/x86/kernel/module.c | 43 > ++++++++++++++++++++++++++++++++++--- > 2 files changed, 42 insertions(+), 5 deletions(-) > > diff --git a/Documentation/kernel-parameters.txt > b/Documentation/kernel-parameters.txt > index 7116fda..580a60c 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -2053,8 +2053,8 @@ bytes respectively. Such letter suffixes can also be > entirely omitted. > IOAPICs that may be present in the system. > > nokaslr [X86] > - Disable kernel base offset ASLR (Address Space > - Layout Randomization) if built into the kernel. > + Disable kernel and module base offset ASLR (Address > + Space Layout Randomization) if built into the kernel. > > noautogroup Disable scheduler automatic task group creation. > > diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c > index 18be189..4948313 100644 > --- a/arch/x86/kernel/module.c > +++ b/arch/x86/kernel/module.c > @@ -28,6 +28,7 @@ > #include <linux/mm.h> > #include <linux/gfp.h> > #include <linux/jump_label.h> > +#include <linux/random.h> > > #include <asm/page.h> > #include <asm/pgtable.h> > @@ -43,13 +44,49 @@ do { > \ > } while (0) > #endif > > +#ifdef CONFIG_RANDOMIZE_BASE > +static unsigned long module_load_offset; > +static int randomize_modules = 1; > + > +static int __init parse_nokaslr(char *p) > +{ > + randomize_modules = 0; > + return 0; > +} > +early_param("nokaslr", parse_nokaslr); > + > +static unsigned long int get_module_load_offset(void) > +{ > + if (randomize_modules) { > + mutex_lock(&module_mutex); > + /* > + * Calculate the module_load_offset the first time this > + * code is called. Once calculated it stays the same until > + * reboot. > + */ > + if (module_load_offset == 0) > + module_load_offset = > + (get_random_int() % 1024 + 1) * PAGE_SIZE; > + mutex_unlock(&module_mutex); > + } > + return module_load_offset; > +} > +#else > +static unsigned long int get_module_load_offset(void) > +{ > + return 0; > +} > +#endif > + > void *module_alloc(unsigned long size) > { > if (PAGE_ALIGN(size) > MODULES_LEN) > return NULL; > - return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END, > - GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC, > - NUMA_NO_NODE, __builtin_return_address(0)); > + return __vmalloc_node_range(size, 1, > + MODULES_VADDR + get_module_load_offset(), > + MODULES_END, GFP_KERNEL | __GFP_HIGHMEM, > + PAGE_KERNEL_EXEC, NUMA_NO_NODE, > + __builtin_return_address(0)); > } > > #ifdef CONFIG_X86_32 > -- _______________________________________________ linux-yocto mailing list [email protected] https://lists.yoctoproject.org/listinfo/linux-yocto
