On Wed, Nov 18, 2015 at 03:20:07PM -0800, Daniel Cashman wrote: > From: dcashman <dcashman@xxxxxxxxxx> > > arm64: arch_mmap_rnd() uses STACK_RND_MASK 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@xxxxxxxxxx> > --- > arch/arm64/Kconfig | 23 +++++++++++++++++++++++ > arch/arm64/mm/mmap.c | 6 ++++-- > 2 files changed, 27 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 9ac16a4..be38e4c 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -51,6 +51,8 @@ config ARM64 > select HAVE_ARCH_JUMP_LABEL > select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP > select HAVE_ARCH_KGDB > + select HAVE_ARCH_MMAP_RND_BITS > + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT > select HAVE_ARCH_SECCOMP_FILTER > select HAVE_ARCH_TRACEHOOK > select HAVE_BPF_JIT > @@ -104,6 +106,27 @@ config ARCH_PHYS_ADDR_T_64BIT > config MMU > def_bool y > > +config ARCH_MMAP_RND_BITS_MIN > + default 15 if ARM64_64K_PAGES > + default 19 > + > +config ARCH_MMAP_RND_BITS_MAX > + default 20 if ARM64_64K_PAGES && ARCH_VA_BITS=39 > + default 24 if ARCH_VA_BITS=39 > + default 23 if ARM64_64K_PAGES && ARCH_VA_BITS=42 > + default 27 if ARCH_VA_BITS=42 > + default 29 if ARM64_64K_PAGES && ARCH_VA_BITS=48 > + default 33 if ARCH_VA_BITS=48 > + default 15 if ARM64_64K_PAGES > + default 19 > + > +config ARCH_MMAP_RND_COMPAT_BITS_MIN > + default 7 if ARM64_64K_PAGES > + default 11 FYI: we now support 16k pages too, so this might need updating. It would be much nicer if this was somehow computed rather than have the results all open-coded like this. Will -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>