On 7/24/19 7:11 PM, Luis Chamberlain wrote:
On Wed, Jul 24, 2019 at 01:58:41AM -0400, Alexandre Ghiti wrote:
diff --git a/mm/util.c b/mm/util.c
index 0781e5575cb3..16f1e56e2996 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -321,7 +321,15 @@ unsigned long randomize_stack_top(unsigned long stack_top)
}
#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
-#ifdef CONFIG_ARCH_HAS_ELF_RANDOMIZE
+unsigned long arch_randomize_brk(struct mm_struct *mm)
+{
+ /* Is the current task 32bit ? */
+ if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
+ return randomize_page(mm->brk, SZ_32M);
+
+ return randomize_page(mm->brk, SZ_1G);
+}
+
unsigned long arch_mmap_rnd(void)
{
unsigned long rnd;
@@ -335,7 +343,6 @@ unsigned long arch_mmap_rnd(void)
return rnd << PAGE_SHIFT;
}
So arch_randomize_brk is no longer ifdef'd around
CONFIG_ARCH_HAS_ELF_RANDOMIZE either and yet the header
still has it. Is that intentional?
Yes, CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT selects
CONFIG_ARCH_HAS_ELF_RANDOMIZE, that's what's new about v4: the generic
functions proposed in this series come with elf randomization.
Alex
Luis
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