[PATCH] strndup_user()

[platform/kernel/linux-arm64.git] / mm / util.c

diff --git a/mm/util.c b/mm/util.c
index 5f4bb59..49e29f7 100644 (file)
--- a/mm/util.c
+++ b/mm/util.c
@@ -1,6 +1,8 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/module.h>
+#include <linux/err.h>
+#include <asm/uaccess.h>
 
 /**
  * kzalloc - allocate memory. The memory is set to zero.
@@ -37,3 +39,38 @@ char *kstrdup(const char *s, gfp_t gfp)
        return buf;
 }
 EXPORT_SYMBOL(kstrdup);
+
+/*
+ * strndup_user - duplicate an existing string from user space
+ *
+ * @s: The string to duplicate
+ * @n: Maximum number of bytes to copy, including the trailing NUL.
+ */
+char *strndup_user(const char __user *s, long n)
+{
+       char *p;
+       long length;
+
+       length = strnlen_user(s, n);
+
+       if (!length)
+               return ERR_PTR(-EFAULT);
+
+       if (length > n)
+               return ERR_PTR(-EINVAL);
+
+       p = kmalloc(length, GFP_KERNEL);
+
+       if (!p)
+               return ERR_PTR(-ENOMEM);
+
+       if (copy_from_user(p, s, length)) {
+               kfree(p);
+               return ERR_PTR(-EFAULT);
+       }
+
+       p[length - 1] = '\0';
+
+       return p;
+}
+EXPORT_SYMBOL(strndup_user);