From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
James Hogan <james.hogan@imgtec.com>,
Pratyush Anand <panand@redhat.com>,
Ingo Molnar <mingo@kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-s390@vger.kernel.org,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
kernel-hardening@lists.openwall.com
Subject: Re: [kernel-hardening] [PATCH 2/4] arm64: Reduce ELF_ET_DYN_BASE
Date: Fri, 23 Jun 2017 06:57:14 +0000 [thread overview]
Message-ID: <CAKv+Gu_2Wg_D+4c3-iqMr9hbKkGVdBtW6Bmxj-4=FOG9hVN5vA@mail.gmail.com> (raw)
In-Reply-To: <1498154792-49952-3-git-send-email-keescook@chromium.org>
Hi Kees,
On 22 June 2017 at 18:06, Kees Cook <keescook@chromium.org> wrote:
> Now that explicitly executed loaders are loaded in the mmap region,
> position PIE binaries lower in the address space to avoid possible
> collisions with mmap or stack regions. For 64-bit, align to 4GB to
> allow runtimes to use the entire 32-bit address space for 32-bit
> pointers.
>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> arch/arm64/include/asm/elf.h | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
> index 5d1700425efe..f742af8f7c42 100644
> --- a/arch/arm64/include/asm/elf.h
> +++ b/arch/arm64/include/asm/elf.h
> @@ -113,12 +113,13 @@
> #define ELF_EXEC_PAGESIZE PAGE_SIZE
>
> /*
> - * This is the location that an ET_DYN program is loaded if exec'ed. Typical
> - * use of this is to invoke "./ld.so someprog" to test out a new version of
> - * the loader. We need to make sure that it is out of the way of the program
> - * that it will "exec", and that there is sufficient room for the brk.
> + * This is the base location for PIE (ET_DYN with INTERP) loads. On
> + * 64-bit, this is raised to 4GB to leave the entire 32-bit address
> + * space open for things that want to use the area for 32-bit pointers.
> */
> -#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3)
> +#define ELF_ET_DYN_BASE (test_thread_flag(TIF_32BIT) ? \
> + 0x000400000UL : \
> + 0x100000000UL)
>
Why are you merging this with the COMPAT definition?
> #ifndef __ASSEMBLY__
>
> @@ -173,8 +174,6 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm,
>
> #ifdef CONFIG_COMPAT
>
> -#define COMPAT_ELF_ET_DYN_BASE (2 * TASK_SIZE_32 / 3)
> -
> /* AArch32 registers. */
> #define COMPAT_ELF_NGREG 18
> typedef unsigned int compat_elf_greg_t;
> --
> 2.7.4
>
next prev parent reply other threads:[~2017-06-23 6:57 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-22 18:06 [PATCH 0/4] Reduce ELF_ET_DYN_BASE Kees Cook
2017-06-22 18:06 ` [PATCH 1/4] arm: " Kees Cook
2017-06-22 18:06 ` [PATCH 2/4] arm64: " Kees Cook
2017-06-23 6:57 ` Ard Biesheuvel [this message]
2017-06-23 13:52 ` [kernel-hardening] " Kees Cook
2017-06-23 14:02 ` Kees Cook
2017-06-23 15:04 ` Ard Biesheuvel
2017-06-22 18:06 ` [PATCH 3/4] powerpc: " Kees Cook
2017-06-23 7:01 ` Michael Ellerman
2017-06-23 20:08 ` Kees Cook
2017-06-26 13:04 ` Michael Ellerman
2017-06-26 18:26 ` Kees Cook
2017-06-22 18:06 ` [PATCH 4/4] s390: " Kees Cook
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