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Date: Wed, 18 Nov 2015 14:48:21 -0800 From: Daniel Cashman <dcashman@...roid.com> To: linux-kernel@...r.kernel.org Cc: linux@....linux.org.uk, akpm@...ux-foundation.org, keescook@...omium.org, mingo@...nel.org, linux-arm-kernel@...ts.infradead.org, corbet@....net, dzickus@...hat.com, ebiederm@...ssion.com, xypron.glpk@....de, jpoimboe@...hat.com, kirill.shutemov@...ux.intel.com, n-horiguchi@...jp.nec.com, aarcange@...hat.com, mgorman@...e.de, tglx@...utronix.de, rientjes@...gle.com, linux-mm@...ck.org, linux-doc@...r.kernel.org, salyzyn@...roid.com, jeffv@...gle.com, nnk@...gle.com, catalin.marinas@....com, will.deacon@....com, hpa@...or.com, x86@...nel.org, hecmargi@....es, bp@...e.de, dcashman@...gle.com Subject: [PATCH 4/4] x86: mm: support ARCH_MMAP_RND_BITS. From: dcashman <dcashman@...gle.com> 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@...gle.com> --- arch/x86/Kconfig | 16 ++++++++++++++++ arch/x86/mm/mmap.c | 12 ++++++------ 2 files changed, 22 insertions(+), 6 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index db3622f..12768c4 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -82,6 +82,8 @@ config X86 select HAVE_ARCH_KASAN if X86_64 && SPARSEMEM_VMEMMAP select HAVE_ARCH_KGDB select HAVE_ARCH_KMEMCHECK + select HAVE_ARCH_MMAP_RND_BITS + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_SOFT_DIRTY if X86_64 select HAVE_ARCH_TRACEHOOK @@ -183,6 +185,20 @@ 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 844b06d..647fecf 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); +#else + rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_bits); +#endif else - rnd = (unsigned long)get_random_int() % (1<<28); + rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_bits); return rnd << PAGE_SHIFT; } -- 2.6.0.rc2.230.g3dd15c0 -- 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/
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