proc: block mounting on top of /proc/<pid>/fd/*

Entries under /proc/<pid>/fd/* are ephemeral and may go away before the
process dies. As such allowing them to be used as mount points creates
the ability to leak mounts that linger until the process dies with no
ability to unmount them until then. Don't allow using them as
mountpoints.

Link: https://lore.kernel.org/r/20240806-work-procfs-v1-5-fb04e1d09f0c@kernel.org
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2024-08-06 18:02:31 +02:00
parent 3836b31c3e
commit 74ce208089
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2

View File

@ -220,8 +220,8 @@ static struct dentry *proc_fd_instantiate(struct dentry *dentry,
ei->op.proc_get_link = proc_fd_link;
tid_fd_update_inode(task, inode, data->mode);
d_set_d_op(dentry, &tid_fd_dentry_operations);
return d_splice_alias(inode, dentry);
return proc_splice_unmountable(inode, dentry,
&tid_fd_dentry_operations);
}
static struct dentry *proc_lookupfd_common(struct inode *dir,