1 files changed, 40 insertions, 8 deletions

diff --git a/mm/util.c b/mm/util.c
index fec39d4509a9..3981ae9d1b15 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -12,10 +12,30 @@
 #include <linux/hugetlb.h>
 #include <linux/vmalloc.h>
 
+#include <asm/sections.h>
 #include <asm/uaccess.h>
 
 #include "internal.h"
 
+static inline int is_kernel_rodata(unsigned long addr)
+{
+	return addr >= (unsigned long)__start_rodata &&
+		addr < (unsigned long)__end_rodata;
+}
+
+/**
+ * kfree_const - conditionally free memory
+ * @x: pointer to the memory
+ *
+ * Function calls kfree only if @x is not in .rodata section.
+ */
+void kfree_const(const void *x)
+{
+	if (!is_kernel_rodata((unsigned long)x))
+		kfree(x);
+}
+EXPORT_SYMBOL(kfree_const);
+
 /**
  * kstrdup - allocate space for and copy an existing string
  * @s: the string to duplicate
@@ -38,6 +58,24 @@ char *kstrdup(const char *s, gfp_t gfp)
 EXPORT_SYMBOL(kstrdup);
 
 /**
+ * kstrdup_const - conditionally duplicate an existing const string
+ * @s: the string to duplicate
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ *
+ * Function returns source string if it is in .rodata section otherwise it
+ * fallbacks to kstrdup.
+ * Strings allocated by kstrdup_const should be freed by kfree_const.
+ */
+const char *kstrdup_const(const char *s, gfp_t gfp)
+{
+	if (is_kernel_rodata((unsigned long)s))
+		return s;
+
+	return kstrdup(s, gfp);
+}
+EXPORT_SYMBOL(kstrdup_const);
+
+/**
  * kstrndup - allocate space for and copy an existing string
  * @s: the string to duplicate
  * @max: read at most @max chars from @s
@@ -240,14 +278,8 @@ int __weak get_user_pages_fast(unsigned long start,
 				int nr_pages, int write, struct page **pages)
 {
 	struct mm_struct *mm = current->mm;
-	int ret;
-
-	down_read(&mm->mmap_sem);
-	ret = get_user_pages(current, mm, start, nr_pages,
-					write, 0, pages, NULL);
-	up_read(&mm->mmap_sem);
-
-	return ret;
+	return get_user_pages_unlocked(current, mm, start, nr_pages,
+				       write, 0, pages);
 }
 EXPORT_SYMBOL_GPL(get_user_pages_fast);