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SubjectRe: [PATCH v3 10/11] mips: Use generic mmap top-down layout
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On 4/18/19 1:31 AM, Kees Cook wrote:
> On Wed, Apr 17, 2019 at 12:33 AM Alexandre Ghiti <alex@ghiti.fr> wrote:
>> mips uses a top-down layout by default that fits the generic functions.
>> At the same time, this commit allows to fix problem uncovered
>> and not fixed for mips here:
>> https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1429066.html
>>
>> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
> Acked-by: Kees Cook <keescook@chromium.org>

Thanks !


>
> -Kees
>
>> ---
>> arch/mips/Kconfig | 1 +
>> arch/mips/include/asm/processor.h | 5 ---
>> arch/mips/mm/mmap.c | 67 -------------------------------
>> 3 files changed, 1 insertion(+), 72 deletions(-)
>>
>> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
>> index 4a5f5b0ee9a9..ec2f07561e4d 100644
>> --- a/arch/mips/Kconfig
>> +++ b/arch/mips/Kconfig
>> @@ -14,6 +14,7 @@ config MIPS
>> select ARCH_USE_CMPXCHG_LOCKREF if 64BIT
>> select ARCH_USE_QUEUED_RWLOCKS
>> select ARCH_USE_QUEUED_SPINLOCKS
>> + select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
>> select ARCH_WANT_IPC_PARSE_VERSION
>> select BUILDTIME_EXTABLE_SORT
>> select CLONE_BACKWARDS
>> diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
>> index aca909bd7841..fba18d4a9190 100644
>> --- a/arch/mips/include/asm/processor.h
>> +++ b/arch/mips/include/asm/processor.h
>> @@ -29,11 +29,6 @@
>>
>> extern unsigned int vced_count, vcei_count;
>>
>> -/*
>> - * MIPS does have an arch_pick_mmap_layout()
>> - */
>> -#define HAVE_ARCH_PICK_MMAP_LAYOUT 1
>> -
>> #ifdef CONFIG_32BIT
>> #ifdef CONFIG_KVM_GUEST
>> /* User space process size is limited to 1GB in KVM Guest Mode */
>> diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
>> index ffbe69f3a7d9..61e65a69bb09 100644
>> --- a/arch/mips/mm/mmap.c
>> +++ b/arch/mips/mm/mmap.c
>> @@ -20,43 +20,6 @@
>> unsigned long shm_align_mask = PAGE_SIZE - 1; /* Sane caches */
>> EXPORT_SYMBOL(shm_align_mask);
>>
>> -/* gap between mmap and stack */
>> -#define MIN_GAP (128*1024*1024UL)
>> -#define MAX_GAP ((STACK_TOP)/6*5)
>> -#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12))
>> -
>> -static int mmap_is_legacy(struct rlimit *rlim_stack)
>> -{
>> - if (current->personality & ADDR_COMPAT_LAYOUT)
>> - return 1;
>> -
>> - if (rlim_stack->rlim_cur == RLIM_INFINITY)
>> - return 1;
>> -
>> - return sysctl_legacy_va_layout;
>> -}
>> -
>> -static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
>> -{
>> - unsigned long gap = rlim_stack->rlim_cur;
>> - unsigned long pad = stack_guard_gap;
>> -
>> - /* Account for stack randomization if necessary */
>> - if (current->flags & PF_RANDOMIZE)
>> - pad += (STACK_RND_MASK << PAGE_SHIFT);
>> -
>> - /* Values close to RLIM_INFINITY can overflow. */
>> - if (gap + pad > gap)
>> - gap += pad;
>> -
>> - if (gap < MIN_GAP)
>> - gap = MIN_GAP;
>> - else if (gap > MAX_GAP)
>> - gap = MAX_GAP;
>> -
>> - return PAGE_ALIGN(STACK_TOP - gap - rnd);
>> -}
>> -
>> #define COLOUR_ALIGN(addr, pgoff) \
>> ((((addr) + shm_align_mask) & ~shm_align_mask) + \
>> (((pgoff) << PAGE_SHIFT) & shm_align_mask))
>> @@ -154,36 +117,6 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
>> addr0, len, pgoff, flags, DOWN);
>> }
>>
>> -unsigned long arch_mmap_rnd(void)
>> -{
>> - unsigned long rnd;
>> -
>> -#ifdef CONFIG_COMPAT
>> - if (TASK_IS_32BIT_ADDR)
>> - rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
>> - else
>> -#endif /* CONFIG_COMPAT */
>> - rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
>> -
>> - return rnd << PAGE_SHIFT;
>> -}
>> -
>> -void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
>> -{
>> - unsigned long random_factor = 0UL;
>> -
>> - if (current->flags & PF_RANDOMIZE)
>> - random_factor = arch_mmap_rnd();
>> -
>> - if (mmap_is_legacy(rlim_stack)) {
>> - mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
>> - mm->get_unmapped_area = arch_get_unmapped_area;
>> - } else {
>> - mm->mmap_base = mmap_base(random_factor, rlim_stack);
>> - mm->get_unmapped_area = arch_get_unmapped_area_topdown;
>> - }
>> -}
>> -
>> static inline unsigned long brk_rnd(void)
>> {
>> unsigned long rnd = get_random_long();
>> --
>> 2.20.1
>>
>

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