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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id o2sm216631pgq.50.2019.05.29.13.10.51 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 29 May 2019 13:10:51 -0700 (PDT) Date: Wed, 29 May 2019 13:10:50 -0700 From: Kees Cook 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 , 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 Subject: Re: [PATCH v4 05/14] arm64, mm: Make randomization selected by generic topdown mmap layout Message-ID: <201905291310.E27265DACF@keescook> References: <20190526134746.9315-1-alex@ghiti.fr> <20190526134746.9315-6-alex@ghiti.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190526134746.9315-6-alex@ghiti.fr> 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 Sun, May 26, 2019 at 09:47:37AM -0400, Alexandre Ghiti wrote: > This commits selects ARCH_HAS_ELF_RANDOMIZE when an arch uses the generic > topdown mmap layout functions so that this security feature is on by > default. > Note that this commit also removes the possibility for arm64 to have elf > randomization and no MMU: without MMU, the security added by randomization > is worth nothing. > > Signed-off-by: Alexandre Ghiti Acked-by: Kees Cook -Kees > --- > arch/Kconfig | 1 + > arch/arm64/Kconfig | 1 - > arch/arm64/kernel/process.c | 8 -------- > mm/util.c | 11 +++++++++-- > 4 files changed, 10 insertions(+), 11 deletions(-) > > diff --git a/arch/Kconfig b/arch/Kconfig > index df3ab04270fa..3732654446cc 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -710,6 +710,7 @@ config HAVE_ARCH_COMPAT_MMAP_BASES > config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > bool > depends on MMU > + select ARCH_HAS_ELF_RANDOMIZE > > config HAVE_COPY_THREAD_TLS > bool > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 3d754c19c11e..403bd3fffdbc 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -15,7 +15,6 @@ config ARM64 > select ARCH_HAS_DMA_MMAP_PGPROT > select ARCH_HAS_DMA_PREP_COHERENT > select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI > - select ARCH_HAS_ELF_RANDOMIZE > select ARCH_HAS_FAST_MULTIPLIER > select ARCH_HAS_FORTIFY_SOURCE > select ARCH_HAS_GCOV_PROFILE_ALL > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index 3767fb21a5b8..3f85f8f2d665 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -535,14 +535,6 @@ unsigned long arch_align_stack(unsigned long sp) > return sp & ~0xf; > } > > -unsigned long arch_randomize_brk(struct mm_struct *mm) > -{ > - if (is_compat_task()) > - return randomize_page(mm->brk, SZ_32M); > - else > - return randomize_page(mm->brk, SZ_1G); > -} > - > /* > * Called from setup_new_exec() after (COMPAT_)SET_PERSONALITY. > */ > diff --git a/mm/util.c b/mm/util.c > index 717f5d75c16e..8a38126edc74 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -319,7 +319,15 @@ unsigned long randomize_stack_top(unsigned long stack_top) > } > > #ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > -#ifdef CONFIG_ARCH_HAS_ELF_RANDOMIZE > +unsigned long arch_randomize_brk(struct mm_struct *mm) > +{ > + /* Is the current task 32bit ? */ > + if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task()) > + return randomize_page(mm->brk, SZ_32M); > + > + return randomize_page(mm->brk, SZ_1G); > +} > + > unsigned long arch_mmap_rnd(void) > { > unsigned long rnd; > @@ -333,7 +341,6 @@ unsigned long arch_mmap_rnd(void) > > return rnd << PAGE_SHIFT; > } > -#endif /* CONFIG_ARCH_HAS_ELF_RANDOMIZE */ > > static int mmap_is_legacy(struct rlimit *rlim_stack) > { > -- > 2.20.1 > -- Kees Cook