[v4,08/10] s390: redefine randomize_et_dyn for ELF_ET_DYN_BASE

Commit Message

Kees Cook March 4, 2015, 9:10 p.m. UTC

In preparation for moving ET_DYN randomization into the ELF loader (which
requires a static ELF_ET_DYN_BASE), this redefines s390's existing ET_DYN
randomization in a call to arch_mmap_rnd(). This refactoring results in
the same ET_DYN randomization on s390.

Signed-off-by: Kees Cook <[e-mail]>
---
 arch/s390/include/asm/elf.h |  8 +++++---
 arch/s390/mm/mmap.c         | 11 ++---------
 2 files changed, 7 insertions(+), 12 deletions(-)

Comments

Martin Schwidefsky March 9, 2015, 5:42 p.m. UTC | #1

On Wed,  4 Mar 2015 13:10:52 -0800
Kees Cook <[e-mail]> wrote:

> In preparation for moving ET_DYN randomization into the ELF loader (which
> requires a static ELF_ET_DYN_BASE), this redefines s390's existing ET_DYN
> randomization in a call to arch_mmap_rnd(). This refactoring results in
> the same ET_DYN randomization on s390.
> 
> Signed-off-by: Kees Cook <[e-mail]>
> ---
>  arch/s390/include/asm/elf.h |  8 +++++---
>  arch/s390/mm/mmap.c         | 11 ++---------
>  2 files changed, 7 insertions(+), 12 deletions(-)

Patch series including this patch works fine
Acked-by: Martin Schwidefsky <[e-mail]>

Patch

diff --git a/arch/s390/include/asm/elf.h b/arch/s390/include/asm/elf.h
index c9df40b5c0ac..2e63de8aac7c 100644
--- a/arch/s390/include/asm/elf.h
+++ b/arch/s390/include/asm/elf.h
@@ -161,10 +161,12 @@  extern unsigned int vdso_enabled;
 /* This is the location that an ET_DYN program is loaded if exec'ed.  Typical
    use of this is to invoke "./ld.so someprog" to test out a new version of
    the loader.  We need to make sure that it is out of the way of the program
-   that it will "exec", and that there is sufficient room for the brk.  */
-
+   that it will "exec", and that there is sufficient room for the brk. 64-bit
+   tasks are aligned to 4GB. */
 extern unsigned long randomize_et_dyn(void);
-#define ELF_ET_DYN_BASE		randomize_et_dyn()
+#define ELF_ET_DYN_BASE (randomize_et_dyn() + (is_32bit_task() ? \
+				(STACK_TOP / 3 * 2) : \
+				(STACK_TOP / 3 * 2) & ~((1UL << 32) - 1)))
 
 /* This yields a mask that user programs can use to figure out what
    instruction set this CPU supports. */
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index a94504d99c47..8c11536f972d 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -179,17 +179,10 @@  arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 
 unsigned long randomize_et_dyn(void)
 {
-	unsigned long base;
-
-	base = STACK_TOP / 3 * 2;
-	if (!is_32bit_task())
-		/* Align to 4GB */
-		base &= ~((1UL << 32) - 1);
-
 	if (current->flags & PF_RANDOMIZE)
-		base += arch_mmap_rnd();
+		return arch_mmap_rnd();
 
-	return base;
+	return 0UL;
 }
 
 #ifndef CONFIG_64BIT