1 files changed, 21 insertions, 0 deletions

diff --git a/kernel/compat.c b/kernel/compat.c
index e167efce842..c9e2ec0b34a 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -1126,3 +1126,24 @@ compat_sys_sysinfo(struct compat_sysinfo __user *info)
 
         return 0;
 }
+
+/*
+ * Allocate user-space memory for the duration of a single system call,
+ * in order to marshall parameters inside a compat thunk.
+ */
+void __user *compat_alloc_user_space(unsigned long len)
+{
+        void __user *ptr;
+
+        /* If len would occupy more than half of the entire compat space... */
+        if (unlikely(len > (((compat_uptr_t)~0) >> 1)))
+                return NULL;
+
+        ptr = arch_compat_alloc_user_space(len);
+
+        if (unlikely(!access_ok(VERIFY_WRITE, ptr, len)))
+                return NULL;
+
+        return ptr;
+}
+EXPORT_SYMBOL_GPL(compat_alloc_user_space);