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    Subject[PATCH 5/5] mm: fold arch_randomize_brk into ARCH_HAS_ELF_RANDOMIZE
    Date
    The arch_randomize_brk() function is used on several architectures,
    even those that don't support ET_DYN ASLR. To avoid bulky extern/#define
    tricks, consolidate the support under CONFIG_ARCH_HAS_ELF_RANDOMIZE for
    the architectures that support it, while still handling CONFIG_COMPAT_BRK.

    Signed-off-by: Kees Cook <keescook@chromium.org>
    ---
    arch/Kconfig | 1 +
    arch/arm/include/asm/elf.h | 4 ----
    arch/arm64/include/asm/elf.h | 4 ----
    arch/mips/include/asm/elf.h | 4 ----
    arch/powerpc/include/asm/elf.h | 4 ----
    arch/s390/include/asm/elf.h | 3 ---
    arch/x86/include/asm/elf.h | 3 ---
    fs/binfmt_elf.c | 4 +---
    include/linux/elf-randomize.h | 12 ++++++++++++
    9 files changed, 14 insertions(+), 25 deletions(-)

    diff --git a/arch/Kconfig b/arch/Kconfig
    index e315cc79ebe7..1c7e98f137db 100644
    --- a/arch/Kconfig
    +++ b/arch/Kconfig
    @@ -490,6 +490,7 @@ config ARCH_HAS_ELF_RANDOMIZE
    An architecture supports choosing randomized locations for
    stack, mmap, brk, and ET_DYN. Defined functions:
    - arch_mmap_rnd(), must respect (current->flags & PF_RANDOMIZE)
    + - arch_randomize_brk()

    #
    # ABI hall of shame
    diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h
    index afb9cafd3786..c1ff8ab12914 100644
    --- a/arch/arm/include/asm/elf.h
    +++ b/arch/arm/include/asm/elf.h
    @@ -125,10 +125,6 @@ int dump_task_regs(struct task_struct *t, elf_gregset_t *elfregs);
    extern void elf_set_personality(const struct elf32_hdr *);
    #define SET_PERSONALITY(ex) elf_set_personality(&(ex))

    -struct mm_struct;
    -extern unsigned long arch_randomize_brk(struct mm_struct *mm);
    -#define arch_randomize_brk arch_randomize_brk
    -
    #ifdef CONFIG_MMU
    #define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
    struct linux_binprm;
    diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
    index f724db00b235..faad6df49e5b 100644
    --- a/arch/arm64/include/asm/elf.h
    +++ b/arch/arm64/include/asm/elf.h
    @@ -156,10 +156,6 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm,
    #define STACK_RND_MASK (0x3ffff >> (PAGE_SHIFT - 12))
    #endif

    -struct mm_struct;
    -extern unsigned long arch_randomize_brk(struct mm_struct *mm);
    -#define arch_randomize_brk arch_randomize_brk
    -
    #ifdef CONFIG_COMPAT

    #ifdef __AARCH64EB__
    diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
    index 535f196ffe02..31d747d46a23 100644
    --- a/arch/mips/include/asm/elf.h
    +++ b/arch/mips/include/asm/elf.h
    @@ -410,10 +410,6 @@ struct linux_binprm;
    extern int arch_setup_additional_pages(struct linux_binprm *bprm,
    int uses_interp);

    -struct mm_struct;
    -extern unsigned long arch_randomize_brk(struct mm_struct *mm);
    -#define arch_randomize_brk arch_randomize_brk
    -
    struct arch_elf_state {
    int fp_abi;
    int interp_fp_abi;
    diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
    index 57d289acb803..ee46ffef608e 100644
    --- a/arch/powerpc/include/asm/elf.h
    +++ b/arch/powerpc/include/asm/elf.h
    @@ -128,10 +128,6 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm,
    (0x7ff >> (PAGE_SHIFT - 12)) : \
    (0x3ffff >> (PAGE_SHIFT - 12)))

    -extern unsigned long arch_randomize_brk(struct mm_struct *mm);
    -#define arch_randomize_brk arch_randomize_brk
    -
    -
    #ifdef CONFIG_SPU_BASE
    /* Notes used in ET_CORE. Note name is "SPU/<fd>/<filename>". */
    #define NT_SPU 1
    diff --git a/arch/s390/include/asm/elf.h b/arch/s390/include/asm/elf.h
    index 617f7fabdb0a..7cc271003ff6 100644
    --- a/arch/s390/include/asm/elf.h
    +++ b/arch/s390/include/asm/elf.h
    @@ -226,9 +226,6 @@ struct linux_binprm;
    #define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
    int arch_setup_additional_pages(struct linux_binprm *, int);

    -extern unsigned long arch_randomize_brk(struct mm_struct *mm);
    -#define arch_randomize_brk arch_randomize_brk
    -
    void *fill_cpu_elf_notes(void *ptr, struct save_area *sa, __vector128 *vxrs);

    #endif
    diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
    index ca3347a9dab5..bbdace22daf8 100644
    --- a/arch/x86/include/asm/elf.h
    +++ b/arch/x86/include/asm/elf.h
    @@ -338,9 +338,6 @@ extern int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
    int uses_interp);
    #define compat_arch_setup_additional_pages compat_arch_setup_additional_pages

    -extern unsigned long arch_randomize_brk(struct mm_struct *mm);
    -#define arch_randomize_brk arch_randomize_brk
    -
    /*
    * True on X86_32 or when emulating IA32 on X86_64
    */
    diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
    index 203c2e6f9a25..96459c18d1eb 100644
    --- a/fs/binfmt_elf.c
    +++ b/fs/binfmt_elf.c
    @@ -1041,15 +1041,13 @@ static int load_elf_binary(struct linux_binprm *bprm)
    current->mm->end_data = end_data;
    current->mm->start_stack = bprm->p;

    -#ifdef arch_randomize_brk
    if ((current->flags & PF_RANDOMIZE) && (randomize_va_space > 1)) {
    current->mm->brk = current->mm->start_brk =
    arch_randomize_brk(current->mm);
    -#ifdef CONFIG_COMPAT_BRK
    +#ifdef compat_brk_randomized
    current->brk_randomized = 1;
    #endif
    }
    -#endif

    if (current->personality & MMAP_PAGE_ZERO) {
    /* Why this, you ask??? Well SVr4 maps page 0 as read-only,
    diff --git a/include/linux/elf-randomize.h b/include/linux/elf-randomize.h
    index 7a4eda02d2b1..b5f0bda9472e 100644
    --- a/include/linux/elf-randomize.h
    +++ b/include/linux/elf-randomize.h
    @@ -1,10 +1,22 @@
    #ifndef _ELF_RANDOMIZE_H
    #define _ELF_RANDOMIZE_H

    +struct mm_struct;
    +
    #ifndef CONFIG_ARCH_HAS_ELF_RANDOMIZE
    static inline unsigned long arch_mmap_rnd(void) { return 0; }
    +# if defined(arch_randomize_brk) && defined(CONFIG_COMPAT_BRK)
    +# define compat_brk_randomized
    +# endif
    +# ifndef arch_randomize_brk
    +# define arch_randomize_brk(mm) (mm->brk)
    +# endif
    #else
    extern unsigned long arch_mmap_rnd(void);
    +extern unsigned long arch_randomize_brk(struct mm_struct *mm);
    +# ifdef CONFIG_COMPAT_BRK
    +# define compat_brk_randomized
    +# endif
    #endif

    #endif
    --
    1.9.1


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