[PATCH] Randomisation: add PF_RANDOMIZE

Even though there is a global flag to disable randomisation, it's useful to
have a per process flag too; the patch below introduces this per process flag
and automatically sets it for "new" binaries.

Eventually we will want to tie this to the legacy-va-space personality
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/binfmt_elf.c

@@ -760,6 +760,8 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
 	if (elf_read_implies_exec(loc->elf_ex, executable_stack))
 		current->personality |= READ_IMPLIES_EXEC;
 
+	if (executable_stack == EXSTACK_DISABLE_X && randomize_va_space)
+		current->flags |= PF_RANDOMIZE;
 	arch_pick_mmap_layout(current->mm);
 
 	/* Do this so that we can load the interpreter, if need be.  We will

fs/exec.c

@@ -877,6 +877,7 @@ int flush_old_exec(struct linux_binprm * bprm)
 	tcomm[i] = '\0';
 	set_task_comm(current, tcomm);
 
+	current->flags &= ~PF_RANDOMIZE;
 	flush_thread();
 
 	if (bprm->e_uid != current->euid || bprm->e_gid != current->egid || 

include/linux/sched.h

@@ -735,6 +735,7 @@ do { if (atomic_dec_and_test(&(tsk)->usage)) __put_task_struct(tsk); } while(0)
 #define PF_LESS_THROTTLE 0x00100000	/* Throttle me less: I clean memory */
 #define PF_SYNCWRITE	0x00200000	/* I am doing a sync write */
 #define PF_BORROWED_MM	0x00400000	/* I am a kthread doing use_mm */
+#define PF_RANDOMIZE	0x00800000	/* randomize virtual address space */
 
 /*
  * Only the _current_ task can read/write to tsk->flags, but other