Messages in this thread Patch in this message | | | Date | Fri, 14 Nov 2014 18:46:20 -0800 | Subject | Re: [PATCH v2] x86, mm: set NX across entire PMD at boot | From | Kees Cook <> |
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On Fri, Nov 14, 2014 at 6:29 PM, Yinghai Lu <yinghai@kernel.org> wrote: > On Fri, Nov 14, 2014 at 5:29 PM, Yinghai Lu <yinghai@kernel.org> wrote: >> On Fri, Nov 14, 2014 at 12:45 PM, Kees Cook <keescook@chromium.org> wrote: >>> v2: >>> - added call to free_init_pages(), as suggested by tglx > >> something is wrong: >> >> [ 7.842479] Freeing unused kernel memory: 3844K (ffffffff82e52000 - >> ffffffff83213000) >> [ 7.843305] Write protecting the kernel read-only data: 28672k > > .... > should use attached one instead. > > 1. should use _brk_end instead of &end, as we only use partial of > brk. > 2. [_brk_end, pm_end) page range is already converted. aka > is not wasted.
Are you sure? For me, _brk_end isn't far enough:
[ 1.475572] all_end: 0xffffffff82df5000 [ 1.476736] _brk_end: 0xffffffff82dd6000
> > --- > arch/x86/mm/init_64.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > Index: linux-2.6/arch/x86/mm/init_64.c > =================================================================== > --- linux-2.6.orig/arch/x86/mm/init_64.c > +++ linux-2.6/arch/x86/mm/init_64.c > @@ -1124,7 +1124,8 @@ void mark_rodata_ro(void) > unsigned long end = (unsigned long) &__end_rodata_hpage_align; > unsigned long text_end = PFN_ALIGN(&__stop___ex_table); > unsigned long rodata_end = PFN_ALIGN(&__end_rodata); > - unsigned long all_end = PFN_ALIGN(&_end); > + unsigned long all_end = PFN_ALIGN(_brk_end); > + unsigned long pmd_end = roundup(all_end, PMD_SIZE); > > printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n", > (end - start) >> 10); > @@ -1136,7 +1137,7 @@ void mark_rodata_ro(void) > * The rodata/data/bss/brk section (but not the kernel text!) > * should also be not-executable. > */ > - set_memory_nx(rodata_start, (all_end - rodata_start) >> PAGE_SHIFT); > + set_memory_nx(rodata_start, (pmd_end - rodata_start) >> PAGE_SHIFT); > > rodata_test(); > > @@ -1148,6 +1149,7 @@ void mark_rodata_ro(void) > set_memory_ro(start, (end-start) >> PAGE_SHIFT); > #endif > > + /* all_end to pmd_end is handled via free_all_bootmem() */ > free_init_pages("unused kernel", > (unsigned long) __va(__pa_symbol(text_end)), > (unsigned long) __va(__pa_symbol(rodata_start)));
This patch produces the same results as my v1 patch:
0xffffffff8202d000-0xffffffff82200000 1868K RW GLB NX pte 0xffffffff82200000-0xffffffff82e00000 12M RW PSE GLB NX pmd 0xffffffff82e00000-0xffffffffc0000000 978M pmd
Is this correct? It sounded like tglx wanted the pmd split, like this:
0xffffffff82200000-0xffffffff82c00000 10M RW PSE GLB NX pmd 0xffffffff82c00000-0xffffffff82df5000 2004K RW GLB NX pte 0xffffffff82df5000-0xffffffff82e00000 44K RW NX pte 0xffffffff82e00000-0xffffffffc0000000 978M pmd
-Kees -- Kees Cook Chrome OS Security
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