x86 get_unmapped_area(): use proper mmap base for bottom-up direction
When the stack is set to unlimited, the bottomup direction is used for
mmap-ings but the mmap_base is not used and thus effectively renders
ASLR for mmapings along with PIE useless.
Cc: Michel Lespinasse <walken@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Sendroiu <molecula2788@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index dbded5a..48f8375 100644
--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -101,7 +101,7 @@
*begin = new_begin;
}
} else {
- *begin = TASK_UNMAPPED_BASE;
+ *begin = mmap_legacy_base();
*end = TASK_SIZE;
}
}
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 62c29a5..f63778c 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -98,7 +98,7 @@
* Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64
* does, but not when emulating X86_32
*/
-static unsigned long mmap_legacy_base(void)
+unsigned long mmap_legacy_base(void)
{
if (mmap_is_ia32())
return TASK_UNMAPPED_BASE;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d722490..923dd6e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -314,6 +314,7 @@
struct user_namespace;
#ifdef CONFIG_MMU
+extern unsigned long mmap_legacy_base(void);
extern void arch_pick_mmap_layout(struct mm_struct *mm);
extern unsigned long
arch_get_unmapped_area(struct file *, unsigned long, unsigned long,