x86: use simpler API for random address requests

Currently, all callers to randomize_range() set the length to 0 and
calculate end by adding a constant to the start address.  We can simplify
the API to remove a bunch of needless checks and variables.

Use the new randomize_addr(start, range) call to set the requested
address.

Link: http://lkml.kernel.org/r/20160803233913.32511-3-jason@lakedaemon.net
Signed-off-by: Jason Cooper <jason@lakedaemon.net>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 28cea7802ecbc456ac3b7f8b8aeb44e0fee00ba0..0888a879120fcb948ec894d96ddee17c36997572 100644 (file)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -509,8 +509,7 @@ unsigned long arch_align_stack(unsigned long sp)
 
 unsigned long arch_randomize_brk(struct mm_struct *mm)
 {
-       unsigned long range_end = mm->brk + 0x02000000;
-       return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
+       return randomize_page(mm->brk, 0x02000000);
 }
 
 /*

diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index 10e0272d789a189b7215100a1d66a676d9b4bbfa..a55ed63b9f91b0d45dbb476a22af9a19c4ab5fc8 100644 (file)
--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -101,7 +101,6 @@ static void find_start_end(unsigned long flags, unsigned long *begin,
                           unsigned long *end)
 {
        if (!test_thread_flag(TIF_ADDR32) && (flags & MAP_32BIT)) {
-               unsigned long new_begin;
                /* This is usually used needed to map code in small
                   model, so it needs to be in the first 31bit. Limit
                   it to that.  This means we need to move the
@@ -112,9 +111,7 @@ static void find_start_end(unsigned long flags, unsigned long *begin,
                *begin = 0x40000000;
                *end = 0x80000000;
                if (current->flags & PF_RANDOMIZE) {
-                       new_begin = randomize_range(*begin, *begin + 0x02000000, 0);
-                       if (new_begin)
-                               *begin = new_begin;
+                       *begin = randomize_page(*begin, 0x02000000);
                }
        } else {
                *begin = current->mm->mmap_legacy_base;