[PATCH] binfmt_elf: randomize PIE binaries (2nd try)

Randomizes -pie compiled binaries from 64k (0x10000) up to ELF_ET_DYN_BASE.

0 -> 64k is excluded to allow NULL ptr accesses to fail.
Signed-off-by: NMarcus Meissner <meissner@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

fs/binfmt_elf.c

@@ -856,7 +856,13 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
 			 * default mmap base, as well as whatever program they
 			 * might try to exec.  This is because the brk will
 			 * follow the loader, and is not movable.  */
-			load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
+			if (current->flags & PF_RANDOMIZE)
+				load_bias = randomize_range(0x10000,
+							    ELF_ET_DYN_BASE,
+							    0);
+			else
+				load_bias = ELF_ET_DYN_BASE;
+			load_bias = ELF_PAGESTART(load_bias - vaddr);
 		}
 
 		error = elf_map(bprm->file, load_bias + vaddr, elf_ppnt,