procfs: make freeing proc_fs_info rcu-delayed

Al Viro · Al Viro · commit e31f0a57ae1a · 2024-02-25T02:10:32.000-05:00
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 &lt;brauner@kernel.org&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
diff --git 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
@@ -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)

Original file line number	Diff line number	Diff line change
`@@ -271,7 +271,7 @@ static void proc_kill_sb(struct super_block *sb)`
`271`	`271`
`272`	`272`	`kill_anon_super(sb);`
`273`	`273`	`put_pid_ns(fs_info->pid_ns);`
`274`		`- kfree(fs_info);`
	`274`	`+ kfree_rcu(fs_info, rcu);`
`275`	`275`	`}`
`276`	`276`
`277`	`277`	`static struct file_system_type proc_fs_type = {`