[PATCH] Improve previous user stack pointer randomisation patch

[PATCH] Improve previous user stack pointer randomisation patch

[Franck Bui-Huu]

This patch improves commit acc6f0110cf735e6c6e0f53736dbb054eafcd13c
by:
    - not using ALMASK to align stack pointer because this macro
      is used for kernel context. The kernel and the application
      are not always compiled with the same ABI.

    - testing PF_RANDOMIZE process flag which is raised when the
      old condition we tested is true.

The first improvement was suggested by Nigel Stephens.

Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
---
 arch/mips/kernel/process.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index bd05f5a..b5b2f31 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -27,7 +27,6 @@
 #include <linux/kallsyms.h>
 #include <linux/random.h>
 
-#include <asm/asm.h>
 #include <asm/bootinfo.h>
 #include <asm/cpu.h>
 #include <asm/dsp.h>
@@ -464,13 +463,14 @@ out:
 }
 
 /*
- * Don't forget that the stack pointer must be aligned on a 8 bytes
- * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
+ * The stack pointer must be aligned on a 8 bytes boundary for 32-bits
+ * ABI and 16 bytes for 64-bits ABI. To make things simple we force to
+ * the maximum alignment required by any ABI.
  */
 unsigned long arch_align_stack(unsigned long sp)
 {
-	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
+	if (current->flags & PF_RANDOMIZE)
 		sp -= get_random_int() & ~PAGE_MASK;
 
-	return sp & ALMASK;
+	return sp & ~0xf;
 }
-- 
1.5.2.3