Messages in this thread Patch in this message | | | Date | Tue, 19 Dec 2017 15:44:01 +0000 | From | Al Viro <> | Subject | Re: [PATCH linux-next] mqueue: fix IPC namespace use-after-free |
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On Tue, Dec 19, 2017 at 03:32:25PM +0000, Al Viro wrote: > + m = mq_internal_mount(); > + if (IS_ERR(m)) > + return ERR_CAST(m); > + atomic_inc(&m->mnt_sb->s_active); > + down_write(&m->mnt_sb->s_umount); > + return dget(m->mnt_root);
Note: this is stripped down mount_subtree(m, ""), of course; it might make sense to recognize that case and bypass the create_mnt_ns/vfs_path_lookup/put_mnt_ns business in mount_subtree() when the relative pathname is empty, replacing it with path.mnt = mntget(mnt); path.dentry = dget(mnt->mnt_root); in such case. That'd allow to simply call mount_subtree() here. It would work as-is, but it's ridiculously heavy for such use right now.
> static int __init init_mqueue_fs(void) > { > + struct vfsmount *m; > int error; > > mqueue_inode_cachep = kmem_cache_create("mqueue_inode_cache", > @@ -1577,6 +1606,10 @@ static int __init init_mqueue_fs(void) > if (error) > goto out_filesystem; > > + m = kern_mount_data(&mqueue_fs_type, &init_ipc_ns); > + if (IS_ERR(m)) > + goto out_filesystem; > + init_ipc_ns.mq_mnt = m; > return 0; > > out_filesystem:
Unrelated issue, but register_filesystem() should be the last thing module_init() of a filesystem driver does. It's a separate story, in any case...
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