procfs: make freeing proc_fs_info rcu-delayed

makes proc_pid_ns() safe from rcu pathwalk (put_pid_ns()
is still synchronous, but that's not a problem - it does
rcu-delay everything that needs to be)

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/proc/root.c b/fs/proc/root.c
index b55dbc7..06a297a 100644 (file)
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -271,7 +271,7 @@ static void proc_kill_sb(struct super_block *sb)
 
        kill_anon_super(sb);
        put_pid_ns(fs_info->pid_ns);
-       kfree(fs_info);
+       kfree_rcu(fs_info, rcu);
 }
 
 static struct file_system_type proc_fs_type = {

diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index de407e7..0b2a898 100644 (file)
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -65,6 +65,7 @@ struct proc_fs_info {
        kgid_t pid_gid;
        enum proc_hidepid hide_pid;
        enum proc_pidonly pidonly;
+       struct rcu_head rcu;
 };
 
 static inline struct proc_fs_info *proc_sb_info(struct super_block *sb)