Fix races around the access to ->s_options

Put generic_show_options read access to s_options under rcu_read_lock,
split save_mount_options() into "we are setting it the first time"
(uses in foo_fill_super()) and "we are relacing and freeing the old one",
synchronize_rcu() before kfree() in the latter.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index ed788426f464..3b534e527e09 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2368,6 +2368,7 @@ extern void file_update_time(struct file *file);
 
 extern int generic_show_options(struct seq_file *m, struct vfsmount *mnt);
 extern void save_mount_options(struct super_block *sb, char *options);
+extern void replace_mount_options(struct super_block *sb, char *options);
 
 static inline ino_t parent_ino(struct dentry *dentry)
 {