Messages in this thread | | | From | Andy Lutomirski <> | Date | Sat, 23 Dec 2017 17:48:49 -0800 | Subject | Re: linux/master crashes on boot with KASAN=y |
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On Sat, Dec 23, 2017 at 4:41 AM, Andrey Ryabinin <aryabinin@virtuozzo.com> wrote: > On 12/23/2017 11:01 AM, Jakub Kicinski wrote: >> Hi! >> >> I bisected a crash on boot to this: >> >> commit 21506525fb8ddb0342f2a2370812d47f6a1f3833 (HEAD, refs/bisect/bad) >> Author: Andy Lutomirski <luto@kernel.org> >> Date: Mon Dec 4 15:07:16 2017 +0100 >> >> x86/kasan/64: Teach KASAN about the cpu_entry_area > > > Thanks. > There is nothing wrong with this patch, it just uncovered older bug. > The actual problem comes from f06bdd4001c2 ("x86/mm: Adapt MODULES_END based on fixmap section size") > which is made kasan_mem_to_shadow(MODULES_END) potentially unaligned to page boundary. > And when we feed unaligned address to kasan_populate_zero_shadow() it doesn't do the right thing. > > Could you tell me if the fix bellow works for you? > > --- > arch/x86/include/asm/kasan.h | 8 ++++++++ > arch/x86/include/asm/pgtable_64_types.h | 4 +++- > 2 files changed, 11 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h > index b577dd0916aa..0c580e4b2ccc 100644 > --- a/arch/x86/include/asm/kasan.h > +++ b/arch/x86/include/asm/kasan.h > @@ -5,6 +5,14 @@ > #include <linux/const.h> > #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) > > +#ifndef KASAN_SHADOW_SCALE_SHIFT > +# ifdef CONFIG_KASAN > +# define KASAN_SHADOW_SCALE_SHIFT 3 > +# else > +# define KASAN_SHADOW_SCALE_SHIFT 0 > +# endif > +#endif > + > /* > * Compiler uses shadow offset assuming that addresses start > * from 0. Kernel addresses don't start from 0, so shadow > diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h > index 6d5f45dcd4a1..d34a90d6c374 100644 > --- a/arch/x86/include/asm/pgtable_64_types.h > +++ b/arch/x86/include/asm/pgtable_64_types.h > @@ -6,6 +6,7 @@ > > #ifndef __ASSEMBLY__ > #include <linux/types.h> > +#include <asm/kasan.h> > #include <asm/kaslr.h> > > /* > @@ -96,7 +97,8 @@ typedef struct { pteval_t pte; } pte_t; > #define VMALLOC_END (VMALLOC_START + _AC((VMALLOC_SIZE_TB << 40) - 1, UL)) > #define MODULES_VADDR (__START_KERNEL_map + KERNEL_IMAGE_SIZE) > /* The module sections ends with the start of the fixmap */ > -#define MODULES_END __fix_to_virt(__end_of_fixed_addresses + 1) > +#define MODULES_END (__fix_to_virt(__end_of_fixed_addresses + 1) & \ > + ~((PAGE_SIZE << KASAN_SHADOW_SCALE_SHIFT) - 1))
Could this be #define MODULES_END KASAN_ROUND_DOWN(__fix_to_virt(...)) instead?
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