1 files changed, 41 insertions, 6 deletions

diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index b0ae85f90f10..1202d5ca2fb5 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -586,6 +586,29 @@ static unsigned long mpx_bd_entry_to_bt_addr(struct mm_struct *mm,
 }
 
 /*
+ * We only want to do a 4-byte get_user() on 32-bit.  Otherwise,
+ * we might run off the end of the bounds table if we are on
+ * a 64-bit kernel and try to get 8 bytes.
+ */
+int get_user_bd_entry(struct mm_struct *mm, unsigned long *bd_entry_ret,
+                long __user *bd_entry_ptr)
+{
+        u32 bd_entry_32;
+        int ret;
+
+        if (is_64bit_mm(mm))
+                return get_user(*bd_entry_ret, bd_entry_ptr);
+
+        /*
+         * Note that get_user() uses the type of the *pointer* to
+         * establish the size of the get, not the destination.
+         */
+        ret = get_user(bd_entry_32, (u32 __user *)bd_entry_ptr);
+        *bd_entry_ret = bd_entry_32;
+        return ret;
+}
+
+/*
  * Get the base of bounds tables pointed by specific bounds
  * directory entry.
  */
@@ -605,7 +628,7 @@ static int get_bt_addr(struct mm_struct *mm,
                 int need_write = 0;
 
                 pagefault_disable();
-                ret = get_user(bd_entry, bd_entry_ptr);
+                ret = get_user_bd_entry(mm, &bd_entry, bd_entry_ptr);
                 pagefault_enable();
                 if (!ret)
                         break;
@@ -700,11 +723,23 @@ static unsigned long mpx_get_bt_entry_offset_bytes(struct mm_struct *mm,
  */
 static inline unsigned long bd_entry_virt_space(struct mm_struct *mm)
 {
-        unsigned long long virt_space = (1ULL << boot_cpu_data.x86_virt_bits);
-        if (is_64bit_mm(mm))
-                return virt_space / MPX_BD_NR_ENTRIES_64;
-        else
-                return virt_space / MPX_BD_NR_ENTRIES_32;
+        unsigned long long virt_space;
+        unsigned long long GB = (1ULL << 30);
+
+        /*
+         * This covers 32-bit emulation as well as 32-bit kernels
+         * running on 64-bit harware.
+         */
+        if (!is_64bit_mm(mm))
+                return (4ULL * GB) / MPX_BD_NR_ENTRIES_32;
+
+        /*
+         * 'x86_virt_bits' returns what the hardware is capable
+         * of, and returns the full >32-bit adddress space when
+         * running 32-bit kernels on 64-bit hardware.
+         */
+        virt_space = (1ULL << boot_cpu_data.x86_virt_bits);
+        return virt_space / MPX_BD_NR_ENTRIES_64;
 }
 
 /*