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[209.85.221.173]) by smtp.gmail.com with ESMTPSA id q128sm329404vke.2.2019.04.17.22.28.46 for (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Wed, 17 Apr 2019 22:28:47 -0700 (PDT) Received: by mail-vk1-f173.google.com with SMTP id 195so209094vkx.9 for ; Wed, 17 Apr 2019 22:28:46 -0700 (PDT) X-Received: by 2002:a1f:7245:: with SMTP id n66mr38243289vkc.40.1555565326448; Wed, 17 Apr 2019 22:28:46 -0700 (PDT) MIME-Version: 1.0 References: <20190417052247.17809-1-alex@ghiti.fr> <20190417052247.17809-8-alex@ghiti.fr> In-Reply-To: <20190417052247.17809-8-alex@ghiti.fr> From: Kees Cook Date: Thu, 18 Apr 2019 00:28:34 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 07/11] arm: Use generic mmap top-down layout To: Alexandre Ghiti Cc: Andrew Morton , Christoph Hellwig , Russell King , Catalin Marinas , Will Deacon , Ralf Baechle , Paul Burton , James Hogan , Palmer Dabbelt , Albert Ou , Alexander Viro , Luis Chamberlain , Kees Cook , LKML , linux-arm-kernel , linux-mips@vger.kernel.org, linux-riscv@lists.infradead.org, "linux-fsdevel@vger.kernel.org" , Linux-MM Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Apr 17, 2019 at 12:30 AM Alexandre Ghiti wrote: > > arm uses a top-down mmap layout by default that exactly fits the generic > functions, so get rid of arch specific code and use the generic version > by selecting ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT. > > Signed-off-by: Alexandre Ghiti Acked-by: Kees Cook -Kees > --- > arch/arm/Kconfig | 1 + > arch/arm/include/asm/processor.h | 2 -- > arch/arm/mm/mmap.c | 62 -------------------------------- > 3 files changed, 1 insertion(+), 64 deletions(-) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 850b4805e2d1..f8f603da181f 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -28,6 +28,7 @@ config ARM > select ARCH_SUPPORTS_ATOMIC_RMW > select ARCH_USE_BUILTIN_BSWAP > select ARCH_USE_CMPXCHG_LOCKREF > + select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU > select ARCH_WANT_IPC_PARSE_VERSION > select BUILDTIME_EXTABLE_SORT if MMU > select CLONE_BACKWARDS > diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h > index 57fe73ea0f72..944ef1fb1237 100644 > --- a/arch/arm/include/asm/processor.h > +++ b/arch/arm/include/asm/processor.h > @@ -143,8 +143,6 @@ static inline void prefetchw(const void *ptr) > #endif > #endif > > -#define HAVE_ARCH_PICK_MMAP_LAYOUT > - > #endif > > #endif /* __ASM_ARM_PROCESSOR_H */ > diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c > index 0b94b674aa91..b8d912ac9e61 100644 > --- a/arch/arm/mm/mmap.c > +++ b/arch/arm/mm/mmap.c > @@ -17,43 +17,6 @@ > ((((addr)+SHMLBA-1)&~(SHMLBA-1)) + \ > (((pgoff)< > -/* 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); > -} > - > /* > * We need to ensure that shared mappings are correctly aligned to > * avoid aliasing issues with VIPT caches. We need to ensure that > @@ -181,31 +144,6 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, > return addr; > } > > -unsigned long arch_mmap_rnd(void) > -{ > - unsigned long rnd; > - > - 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; > - } > -} > - > /* > * You really shouldn't be using read() or write() on /dev/mem. This > * might go away in the future. > -- > 2.20.1 > -- Kees Cook