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, 2 deletions

diff --git a/drivers/isdn/capi/capifs.c b/drivers/isdn/capi/capifs.c
index b129409925af..8f9f3b5a3e8c 100644
--- a/drivers/isdn/capi/capifs.c
+++ b/drivers/isdn/capi/capifs.c
@@ -75,8 +75,7 @@ static int capifs_remount(struct super_block *s, int *flags, char *data)
                 }
         }
 
-        kfree(s->s_options);
-        s->s_options = new_opt;
+        replace_mount_options(s, new_opt);
 
         config.setuid  = setuid;
         config.setgid  = setgid;