| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <CAGXu5jL7GXKqj1UTpwEwtZ_kKpeorA0fz84Pq=15kdZ3vGytQA@mail.gmail.com>
Date: Wed, 18 Nov 2015 15:18:07 -0800
From: Kees Cook <keescook@...omium.org>
To: Daniel Cashman <dcashman@...roid.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Russell King - ARM Linux <linux@....linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...nel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
Jonathan Corbet <corbet@....net>,
Don Zickus <dzickus@...hat.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Heinrich Schuchardt <xypron.glpk@....de>, jpoimboe@...hat.com,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
n-horiguchi@...jp.nec.com, Andrea Arcangeli <aarcange@...hat.com>,
Mel Gorman <mgorman@...e.de>,
Thomas Gleixner <tglx@...utronix.de>,
David Rientjes <rientjes@...gle.com>,
Linux-MM <linux-mm@...ck.org>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
Mark Salyzyn <salyzyn@...roid.com>,
Jeffrey Vander Stoep <jeffv@...gle.com>,
Nick Kralevich <nnk@...gle.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
"H. Peter Anvin" <hpa@...or.com>,
"x86@...nel.org" <x86@...nel.org>, Hector Marco <hecmargi@....es>,
Borislav Petkov <bp@...e.de>,
Daniel Cashman <dcashman@...gle.com>
Subject: Re: [PATCH 1/4] mm: mmap: Add new /proc tunable for mmap_base ASLR.
On Wed, Nov 18, 2015 at 2:48 PM, Daniel Cashman <dcashman@...roid.com> wrote:
> From: dcashman <dcashman@...gle.com>
>
> ASLR currently only uses 8 bits to generate the random offset for the
> mmap base address on 32 bit architectures. This value was chosen to
> prevent a poorly chosen value from dividing the address space in such
> a way as to prevent large allocations. This may not be an issue on all
> platforms. Allow the specification of a minimum number of bits so that
> platforms desiring greater ASLR protection may determine where to place
> the trade-off.
>
> Signed-off-by: Daniel Cashman <dcashman@...gle.com>
> ---
> Documentation/sysctl/vm.txt | 29 ++++++++++++++++++++
> arch/Kconfig | 64 +++++++++++++++++++++++++++++++++++++++++++++
> include/linux/mm.h | 11 ++++++++
> kernel/sysctl.c | 22 ++++++++++++++++
> mm/mmap.c | 12 +++++++++
> 5 files changed, 138 insertions(+)
>
> diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
> index f72370b..d77a81a 100644
> --- a/Documentation/sysctl/vm.txt
> +++ b/Documentation/sysctl/vm.txt
> @@ -42,6 +42,8 @@ Currently, these files are in /proc/sys/vm:
> - min_slab_ratio
> - min_unmapped_ratio
> - mmap_min_addr
> +- mmap_rnd_bits
> +- mmap_rnd_compat_bits
> - nr_hugepages
> - nr_overcommit_hugepages
> - nr_trim_pages (only if CONFIG_MMU=n)
> @@ -485,6 +487,33 @@ against future potential kernel bugs.
>
> ==============================================================
>
> +mmap_rnd_bits:
> +
> +This value can be used to select the number of bits to use to
> +determine the random offset to the base address of vma regions
> +resulting from mmap allocations on architectures which support
> +tuning address space randomization. This value will be bounded
> +by the architecture's minimum and maximum supported values.
> +
> +This value can be changed after boot using the
> +/proc/sys/kernel/mmap_rnd_bits tunable
Here and several places below also need the swap from
"/proc/sys/kernel/..." to ".../vm/...".
> +
> +==============================================================
> +
> +mmap_rnd_compat_bits:
> +
> +This value can be used to select the number of bits to use to
> +determine the random offset to the base address of vma regions
> +resulting from mmap allocations for applications run in
> +compatibility mode on architectures which support tuning address
> +space randomization. This value will be bounded by the
> +architecture's minimum and maximum supported values.
> +
> +This value can be changed after boot using the
> +/proc/sys/kernel/mmap_rnd_compat_bits tunable
> +
> +==============================================================
> +
> nr_hugepages
>
> Change the minimum size of the hugepage pool.
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 4e949e5..141823f 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -511,6 +511,70 @@ config ARCH_HAS_ELF_RANDOMIZE
> - arch_mmap_rnd()
> - arch_randomize_brk()
>
> +config HAVE_ARCH_MMAP_RND_BITS
> + bool
> + help
> + An arch should select this symbol if it supports setting a variable
> + number of bits for use in establishing the base address for mmap
> + allocations and provides values for both:
> + - ARCH_MMAP_RND_BITS_MIN
> + - ARCH_MMAP_RND_BITS_MAX
> +
> +config ARCH_MMAP_RND_BITS_MIN
> + int
> +
> +config ARCH_MMAP_RND_BITS_MAX
> + int
> +
> +config ARCH_MMAP_RND_BITS_DEFAULT
> + int
> +
> +config ARCH_MMAP_RND_BITS
> + int "Number of bits to use for ASLR of mmap base address" if EXPERT
> + range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
> + default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
> + default ARCH_MMAP_RND_BITS_MIN
> + depends on HAVE_ARCH_MMAP_RND_BITS
> + help
> + This value can be used to select the number of bits to use to
> + determine the random offset to the base address of vma regions
> + resulting from mmap allocations. This value will be bounded
> + by the architecture's minimum and maximum supported values.
> +
> + This value can be changed after boot using the
> + /proc/sys/kernel/mmap_rnd_bits tunable
> +
> +config HAVE_ARCH_MMAP_RND_COMPAT_BITS
> + bool
> + help
> + An arch should select this symbol if it supports running applications
> + in compatibility mode, supports setting a variable number of bits for
> + use in establishing the base address for mmap allocations, and
> + provides values for both:
> + - ARCH_MMAP_RND_COMPAT_BITS_MIN
> + - ARCH_MMAP_RND_COMPAT_BITS_MAX
> +
> +config ARCH_MMAP_RND_COMPAT_BITS_MIN
> + int
> +
> +config ARCH_MMAP_RND_COMPAT_BITS_MAX
> + int
> +
> +config ARCH_MMAP_RND_COMPAT_BITS
> + int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
> + range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
> + default ARCH_MMAP_RND_COMPAT_BITS_MIN
> + depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
> + help
> + This value can be used to select the number of bits to use to
> + determine the random offset to the base address of vma regions
> + resulting from mmap allocations for compatible applications This
> + value will be bounded by the architecture's minimum and maximum
> + supported values.
> +
> + This value can be changed after boot using the
> + /proc/sys/kernel/mmap_rnd_compat_bits tunable
> +
> config HAVE_COPY_THREAD_TLS
> bool
> help
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 00bad77..7d39828 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -51,6 +51,17 @@ extern int sysctl_legacy_va_layout;
> #define sysctl_legacy_va_layout 0
> #endif
>
> +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
> +extern int mmap_rnd_bits_min;
> +extern int mmap_rnd_bits_max;
> +extern int mmap_rnd_bits;
> +#endif
> +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
> +extern int mmap_rnd_compat_bits_min;
> +extern int mmap_rnd_compat_bits_max;
> +extern int mmap_rnd_compat_bits;
> +#endif
> +
> #include <asm/page.h>
> #include <asm/pgtable.h>
> #include <asm/processor.h>
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index dc6858d..40e5de6 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1568,6 +1568,28 @@ static struct ctl_table vm_table[] = {
> .mode = 0644,
> .proc_handler = proc_doulongvec_minmax,
> },
> +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
> + {
> + .procname = "mmap_rnd_bits",
> + .data = &mmap_rnd_bits,
> + .maxlen = sizeof(mmap_rnd_bits),
> + .mode = 0644,
> + .proc_handler = proc_dointvec_minmax,
> + .extra1 = &mmap_rnd_bits_min,
> + .extra2 = &mmap_rnd_bits_max,
> + },
> +#endif
> +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
> + {
> + .procname = "mmap_rnd_compat_bits",
> + .data = &mmap_rnd_compat_bits,
> + .maxlen = sizeof(mmap_rnd_compat_bits),
> + .mode = 0644,
> + .proc_handler = proc_dointvec_minmax,
> + .extra1 = &mmap_rnd_compat_bits_min,
> + .extra2 = &mmap_rnd_compat_bits_max,
> + },
> +#endif
> { }
> };
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 2ce04a6..aa49841 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -58,6 +58,18 @@
> #define arch_rebalance_pgtables(addr, len) (addr)
> #endif
>
> +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
> +int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
> +int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
> +int mmap_rnd_bits = CONFIG_ARCH_MMAP_RND_BITS;
> +#endif
> +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
> +int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN;
> +int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
I think the min/max values should be const, since they're determined
at build time and should never change.
> +int mmap_rnd_compat_bits = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
> +#endif
> +
> +
> static void unmap_region(struct mm_struct *mm,
> struct vm_area_struct *vma, struct vm_area_struct *prev,
> unsigned long start, unsigned long end);
> --
> 2.6.0.rc2.230.g3dd15c0
>
-Kees
--
Kees Cook
Chrome OS Security
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists