Re: [PATCH v3 10/11] mips: Use generic mmap top-down layout

From: Alex Ghiti <alex@ghiti.fr>
To: Kees Cook <keescook@chromium.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Palmer Dabbelt <palmer@sifive.com>,
	Will Deacon <will.deacon@arm.com>,
	Russell King <linux@armlinux.org.uk>,
	Ralf Baechle <ralf@linux-mips.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>, Paul Burton <paul.burton@mips.com>,
	linux-riscv@lists.infradead.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	James Hogan <jhogan@kernel.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mips@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Luis Chamberlain <mcgrof@kernel.org>
Subject: Re: [PATCH v3 10/11] mips: Use generic mmap top-down layout
Date: Thu, 18 Apr 2019 02:08:31 -0400	[thread overview]
Message-ID: <82116ac6-1997-b52d-b1dd-98cc97e731bf@ghiti.fr> (raw)
In-Reply-To: <CAGXu5jJSgHKjrQ2Z-aKofqroUDBjPnLOjiORw9pHT_cANhAqpg@mail.gmail.com>

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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