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[217.70.178.230]) by mx.google.com with ESMTPS id p6si10031930ejg.75.2019.08.07.23.26.51 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 07 Aug 2019 23:26:51 -0700 (PDT) Received-SPF: neutral (google.com: 217.70.178.230 is neither permitted nor denied by best guess record for domain of alex@ghiti.fr) client-ip=217.70.178.230; Authentication-Results: mx.google.com; spf=neutral (google.com: 217.70.178.230 is neither permitted nor denied by best guess record for domain of alex@ghiti.fr) smtp.mailfrom=alex@ghiti.fr Received: from alex.numericable.fr (127.19.86.79.rev.sfr.net [79.86.19.127]) (Authenticated sender: alex@ghiti.fr) by relay10.mail.gandi.net (Postfix) with ESMTPSA id A9D96240006; Thu, 8 Aug 2019 06:26:45 +0000 (UTC) From: Alexandre Ghiti To: Andrew Morton Cc: Paul Walmsley , Luis Chamberlain , Christoph Hellwig , Russell King , Catalin Marinas , Will Deacon , Ralf Baechle , Paul Burton , James Hogan , Palmer Dabbelt , Albert Ou , Alexander Viro , Kees Cook , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Alexandre Ghiti Subject: [PATCH v6 08/14] arm: Use generic mmap top-down layout and brk randomization Date: Thu, 8 Aug 2019 02:17:50 -0400 Message-Id: <20190808061756.19712-9-alex@ghiti.fr> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190808061756.19712-1-alex@ghiti.fr> References: <20190808061756.19712-1-alex@ghiti.fr> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: 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. As ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT selects ARCH_HAS_ELF_RANDOMIZE, use the generic version of arch_randomize_brk since it also fits. Note that this commit also removes the possibility for arm to have elf randomization and no MMU: without MMU, the security added by randomization is worth nothing. Note that it is safe to remove STACK_RND_MASK since it matches the default value. Signed-off-by: Alexandre Ghiti Acked-by: Kees Cook Reviewed-by: Luis Chamberlain --- arch/arm/Kconfig | 2 +- arch/arm/include/asm/processor.h | 2 -- arch/arm/kernel/process.c | 5 --- arch/arm/mm/mmap.c | 62 -------------------------------- 4 files changed, 1 insertion(+), 70 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 33b00579beff..81b08b027e4e 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -7,7 +7,6 @@ config ARM select ARCH_HAS_BINFMT_FLAT select ARCH_HAS_DEBUG_VIRTUAL if MMU select ARCH_HAS_DEVMEM_IS_ALLOWED - select ARCH_HAS_ELF_RANDOMIZE select ARCH_HAS_FORTIFY_SOURCE select ARCH_HAS_KEEPINITRD select ARCH_HAS_KCOV @@ -30,6 +29,7 @@ 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 BINFMT_FLAT_ARGVP_ENVP_ON_STACK select BUILDTIME_EXTABLE_SORT if MMU diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h index 20c2f42454b8..614bf829e454 100644 --- a/arch/arm/include/asm/processor.h +++ b/arch/arm/include/asm/processor.h @@ -140,8 +140,6 @@ 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/kernel/process.c b/arch/arm/kernel/process.c index f934a6739fc0..9485acc520a4 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -319,11 +319,6 @@ unsigned long get_wchan(struct task_struct *p) return 0; } -unsigned long arch_randomize_brk(struct mm_struct *mm) -{ - return randomize_page(mm->brk, 0x02000000); -} - #ifdef CONFIG_MMU #ifdef CONFIG_KUSER_HELPERS /* 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)<> (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