1 files changed, 37 insertions, 5 deletions

diff --git a/mm/util.c b/mm/util.c
index d7b1065644be..4d59b4ffe66b 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -80,6 +80,8 @@ EXPORT_SYMBOL(kstrdup_const);
  * @s: the string to duplicate
  * @max: read at most @max chars from @s
  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ *
+ * Note: Use kmemdup_nul() instead if the size is known exactly.
  */
 char *kstrndup(const char *s, size_t max, gfp_t gfp)
 {
@@ -118,6 +120,28 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp)
 EXPORT_SYMBOL(kmemdup);
 
 /**
+ * kmemdup_nul - Create a NUL-terminated string from unterminated data
+ * @s: The data to stringify
+ * @len: The size of the data
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ */
+char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
+{
+	char *buf;
+
+	if (!s)
+		return NULL;
+
+	buf = kmalloc_track_caller(len + 1, gfp);
+	if (buf) {
+		memcpy(buf, s, len);
+		buf[len] = '\0';
+	}
+	return buf;
+}
+EXPORT_SYMBOL(kmemdup_nul);
+
+/**
  * memdup_user - duplicate memory region from user space
  *
  * @src: source address in user space
@@ -254,7 +278,7 @@ int __weak get_user_pages_fast(unsigned long start,
 {
 	struct mm_struct *mm = current->mm;
 	return get_user_pages_unlocked(current, mm, start, nr_pages,
-				       write, 0, pages);
+				       pages, write ? FOLL_WRITE : 0);
 }
 EXPORT_SYMBOL_GPL(get_user_pages_fast);
 
@@ -405,17 +429,25 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
 	int res = 0;
 	unsigned int len;
 	struct mm_struct *mm = get_task_mm(task);
+	unsigned long arg_start, arg_end, env_start, env_end;
 	if (!mm)
 		goto out;
 	if (!mm->arg_end)
 		goto out_mm;	/* Shh! No looking before we're done */
 
-	len = mm->arg_end - mm->arg_start;
+	down_read(&mm->mmap_sem);
+	arg_start = mm->arg_start;
+	arg_end = mm->arg_end;
+	env_start = mm->env_start;
+	env_end = mm->env_end;
+	up_read(&mm->mmap_sem);
+
+	len = arg_end - arg_start;
 
 	if (len > buflen)
 		len = buflen;
 
-	res = access_process_vm(task, mm->arg_start, buffer, len, 0);
+	res = access_process_vm(task, arg_start, buffer, len, 0);
 
 	/*
 	 * If the nul at the end of args has been overwritten, then
@@ -426,10 +458,10 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
 		if (len < res) {
 			res = len;
 		} else {
-			len = mm->env_end - mm->env_start;
+			len = env_end - env_start;
 			if (len > buflen - res)
 				len = buflen - res;
-			res += access_process_vm(task, mm->env_start,
+			res += access_process_vm(task, env_start,
 						 buffer+res, len, 0);
 			res = strnlen(buffer, res);
 		}