fs: namespace: suppress 'may be used uninitialized' warnings

commit b8850d1fa8e2f6653e57daf6d08e58c5f5eb2c85 upstream.

The gcc version 4.9.1 compiler complains Even though it isn't possible for
these variables to not get initialized before they are used.

fs/namespace.c: In function ‘SyS_mount’:
fs/namespace.c:2720:8: warning: ‘kernel_dev’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
        ^
fs/namespace.c:2699:8: note: ‘kernel_dev’ was declared here
  char *kernel_dev;
        ^
fs/namespace.c:2720:8: warning: ‘kernel_type’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
        ^
fs/namespace.c:2697:8: note: ‘kernel_type’ was declared here
  char *kernel_type;
        ^

Fix the warnings by simplifying copy_mount_string() as suggested by Al Viro.

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

1 files changed, 8 insertions, 18 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 185cd1aefa14..9ae6837ef5bf 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2323,21 +2323,9 @@ int copy_mount_options(const void __user * data, unsigned long *where)
 	return 0;
 }
 
-int copy_mount_string(const void __user *data, char **where)
+char *copy_mount_string(const void __user *data)
 {
-	char *tmp;
-
-	if (!data) {
-		*where = NULL;
-		return 0;
-	}
-
-	tmp = strndup_user(data, PAGE_SIZE);
-	if (IS_ERR(tmp))
-		return PTR_ERR(tmp);
-
-	*where = tmp;
-	return 0;
+	return data ? strndup_user(data, PAGE_SIZE) : NULL;
 }
 
 /*
@@ -2617,8 +2605,9 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
 	char *kernel_dev;
 	unsigned long data_page;
 
-	ret = copy_mount_string(type, &kernel_type);
-	if (ret < 0)
+	kernel_type = copy_mount_string(type);
+	ret = PTR_ERR(kernel_type);
+	if (IS_ERR(kernel_type))
 		goto out_type;
 
 	kernel_dir = getname(dir_name);
@@ -2627,8 +2616,9 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
 		goto out_dir;
 	}
 
-	ret = copy_mount_string(dev_name, &kernel_dev);
-	if (ret < 0)
+	kernel_dev = copy_mount_string(dev_name);
+	ret = PTR_ERR(kernel_dev);
+	if (IS_ERR(kernel_dev))
 		goto out_dev;
 
 	ret = copy_mount_options(data, &data_page);