diff options
| author | Daniel Cashman <dcashman@google.com> | 2016-01-14 15:20:06 -0800 |
|---|---|---|
| committer | Kees Cook <keescook@google.com> | 2016-03-24 12:45:34 -0700 |
| commit | cba1ca8ddc9800e7b76eeb5d8b58aa86637ec57d (patch) | |
| tree | 3bedc084d4273fc7e84733cc7c3ca04e84b6b7f7 | |
| parent | d5ee05798c3f64a7f2ae46cbb69400c073bd85b5 (diff) | |
| download | v4.1-cba1ca8ddc9800e7b76eeb5d8b58aa86637ec57d.tar.gz | |
BACKPORT: x86: mm: support ARCH_MMAP_RND_BITS
x86: arch_mmap_rnd() uses hard-coded values, 8 for 32-bit and 28 for
64-bit, to generate the random offset for the mmap base address. This
value represents a compromise between increased ASLR effectiveness and
avoiding address-space fragmentation. Replace it with a Kconfig option,
which is sensibly bounded, so that platform developers may choose where
to place this compromise. Keep default values as new minimums.
Signed-off-by: Daniel Cashman <dcashman@google.com>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Jeff Vander Stoep <jeffv@google.com>
Cc: Nick Kralevich <nnk@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Hector Marco-Gisbert <hecmargi@upv.es>
Cc: Borislav Petkov <bp@suse.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Bug: 27796957
Patchset: ASLR sysctl
(cherry picked from commit 9e08f57d684ac2f40685f55f659564bfd91a971e)
Signed-off-by: Kees Cook <keescook@google.com>
Change-Id: I8e7bbdd1eb5144c13953f10867a39a4cf59da6b0
| -rw-r--r-- | arch/x86/Kconfig | 16 | ||||
| -rw-r--r-- | arch/x86/mm/mmap.c | 12 |
2 files changed, 22 insertions, 6 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 226d5696e1d..307f42d34cd 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -44,6 +44,8 @@ config X86 select ARCH_DISCARD_MEMBLOCK select ARCH_WANT_OPTIONAL_GPIOLIB select ARCH_WANT_FRAME_POINTERS + select HAVE_ARCH_MMAP_RND_BITS if MMU + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT select HAVE_DMA_ATTRS select HAVE_DMA_CONTIGUOUS select HAVE_KRETPROBES @@ -174,6 +176,20 @@ config HAVE_LATENCYTOP_SUPPORT config MMU def_bool y +config ARCH_MMAP_RND_BITS_MIN + default 28 if 64BIT + default 8 + +config ARCH_MMAP_RND_BITS_MAX + default 32 if 64BIT + default 16 + +config ARCH_MMAP_RND_COMPAT_BITS_MIN + default 8 + +config ARCH_MMAP_RND_COMPAT_BITS_MAX + default 16 + config SBUS bool diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 9d518d693b4..f3c8b75827b 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -69,14 +69,14 @@ unsigned long arch_mmap_rnd(void) { unsigned long rnd; - /* - * 8 bits of randomness in 32bit mmaps, 20 address space bits - * 28 bits of randomness in 64bit mmaps, 40 address space bits - */ if (mmap_is_ia32()) - rnd = (unsigned long)get_random_int() % (1<<8); +#ifdef CONFIG_COMPAT + rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_compat_bits) - 1); +#else + rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_bits) - 1); +#endif else - rnd = (unsigned long)get_random_int() % (1<<28); + rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_bits) - 1); return rnd << PAGE_SHIFT; } |