1 files changed, 88 insertions, 37 deletions

diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 7940166c799b..19ad095b41df 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -30,30 +30,44 @@
 #include <linux/limits.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/mm.h>
+#include <linux/compat.h>
 #include <asm/elf.h>
 
 struct va_alignment __read_mostly va_align = {
 	.flags = -1,
 };
 
-static unsigned long stack_maxrandom_size(void)
+unsigned long tasksize_32bit(void)
+{
+	return IA32_PAGE_OFFSET;
+}
+
+unsigned long tasksize_64bit(void)
+{
+	return TASK_SIZE_MAX;
+}
+
+static unsigned long stack_maxrandom_size(unsigned long task_size)
 {
 	unsigned long max = 0;
 	if ((current->flags & PF_RANDOMIZE) &&
 		!(current->personality & ADDR_NO_RANDOMIZE)) {
-		max = ((-1UL) & STACK_RND_MASK) << PAGE_SHIFT;
+		max = (-1UL) & __STACK_RND_MASK(task_size == tasksize_32bit());
+		max <<= PAGE_SHIFT;
 	}
 
 	return max;
 }
 
-/*
- * Top of mmap area (just below the process stack).
- *
- * Leave an at least ~128 MB hole with possible stack randomization.
- */
-#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())
-#define MAX_GAP (TASK_SIZE/6*5)
+#ifdef CONFIG_COMPAT
+# define mmap32_rnd_bits  mmap_rnd_compat_bits
+# define mmap64_rnd_bits  mmap_rnd_bits
+#else
+# define mmap32_rnd_bits  mmap_rnd_bits
+# define mmap64_rnd_bits  mmap_rnd_bits
+#endif
+
+#define SIZE_128M    (128 * 1024 * 1024UL)
 
 static int mmap_is_legacy(void)
 {
@@ -66,54 +80,91 @@ static int mmap_is_legacy(void)
 	return sysctl_legacy_va_layout;
 }
 
-unsigned long arch_mmap_rnd(void)
+static unsigned long arch_rnd(unsigned int rndbits)
 {
-	unsigned long rnd;
-
-	if (mmap_is_ia32())
-#ifdef CONFIG_COMPAT
-		rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
-#else
-		rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
-#endif
-	else
-		rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
+	return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT;
+}
 
-	return rnd << PAGE_SHIFT;
+unsigned long arch_mmap_rnd(void)
+{
+	if (!(current->flags & PF_RANDOMIZE))
+		return 0;
+	return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);
 }
 
-static unsigned long mmap_base(unsigned long rnd)
+static unsigned long mmap_base(unsigned long rnd, unsigned long task_size)
 {
 	unsigned long gap = rlimit(RLIMIT_STACK);
+	unsigned long gap_min, gap_max;
+
+	/*
+	 * Top of mmap area (just below the process stack).
+	 * Leave an at least ~128 MB hole with possible stack randomization.
+	 */
+	gap_min = SIZE_128M + stack_maxrandom_size(task_size);
+	gap_max = (task_size / 6) * 5;
 
-	if (gap < MIN_GAP)
-		gap = MIN_GAP;
-	else if (gap > MAX_GAP)
-		gap = MAX_GAP;
+	if (gap < gap_min)
+		gap = gap_min;
+	else if (gap > gap_max)
+		gap = gap_max;
+
+	return PAGE_ALIGN(task_size - gap - rnd);
+}
 
-	return PAGE_ALIGN(TASK_SIZE - gap - rnd);
+static unsigned long mmap_legacy_base(unsigned long rnd,
+				      unsigned long task_size)
+{
+	return __TASK_UNMAPPED_BASE(task_size) + rnd;
 }
 
 /*
  * This function, called very early during the creation of a new
  * process VM image, sets up which VM layout function to use:
  */
+static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base,
+		unsigned long random_factor, unsigned long task_size)
+{
+	*legacy_base = mmap_legacy_base(random_factor, task_size);
+	if (mmap_is_legacy())
+		*base = *legacy_base;
+	else
+		*base = mmap_base(random_factor, task_size);
+}
+
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
-	unsigned long random_factor = 0UL;
+	if (mmap_is_legacy())
+		mm->get_unmapped_area = arch_get_unmapped_area;
+	else
+		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 
-	if (current->flags & PF_RANDOMIZE)
-		random_factor = arch_mmap_rnd();
+	arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base,
+			arch_rnd(mmap64_rnd_bits), tasksize_64bit());
+
+#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
+	/*
+	 * The mmap syscall mapping base decision depends solely on the
+	 * syscall type (64-bit or compat). This applies for 64bit
+	 * applications and 32bit applications. The 64bit syscall uses
+	 * mmap_base, the compat syscall uses mmap_compat_base.
+	 */
+	arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base,
+			arch_rnd(mmap32_rnd_bits), tasksize_32bit());
+#endif
+}
 
-	mm->mmap_legacy_base = TASK_UNMAPPED_BASE + random_factor;
+unsigned long get_mmap_base(int is_legacy)
+{
+	struct mm_struct *mm = current->mm;
 
-	if (mmap_is_legacy()) {
-		mm->mmap_base = mm->mmap_legacy_base;
-		mm->get_unmapped_area = arch_get_unmapped_area;
-	} else {
-		mm->mmap_base = mmap_base(random_factor);
-		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
+#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
+	if (in_compat_syscall()) {
+		return is_legacy ? mm->mmap_compat_legacy_base
+				 : mm->mmap_compat_base;
 	}
+#endif
+	return is_legacy ? mm->mmap_legacy_base : mm->mmap_base;
 }
 
 const char *arch_vma_name(struct vm_area_struct *vma)