[Devel] Re: namespace and nsproxy syscalls

[Serge E. Hallyn]

Quoting Cedric Le Goater (clg at fr.ibm.com):

Looks ok, except for maintainability the following change might make
sense:

> +asmlinkage long sys_unshare_ns(unsigned long unshare_ns_flags)
> +{
> +	int err = 0;
> +	struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
> +	struct fs_struct *fs, *new_fs = NULL;
> +	struct mnt_namespace *mnt, *new_mnt = NULL;
> +	struct uts_namespace *uts, *new_uts = NULL;
> +	struct ipc_namespace *ipc, *new_ipc = NULL;
> +	unsigned long unshare_flags = 0;
> +
> +	/* Return -EINVAL for all unsupported flags */
> +	err = -EINVAL;
> +	if (unshare_ns_flags & ~(UNSHARE_NS_MNT|UNSHARE_NS_UTS|UNSHARE_NS_IPC|
> +				 UNSHARE_NS_USER|UNSHARE_NS_NET|
> +				 UNSHARE_NS_PID))
> +		goto bad_unshare_ns_out;

Get rid of this explicit check against unshare_ns_flags, and

> +	/* convert unshare_ns flags to clone flags */
> +	if (unshare_ns_flags & UNSHARE_NS_MNT)
> +		unshare_flags |= CLONE_NEWNS|CLONE_FS;
> +	if (unshare_ns_flags & UNSHARE_NS_UTS)
> +		unshare_flags |= CLONE_NEWUTS;
> +	if (unshare_ns_flags & UNSHARE_NS_IPC)
> +		unshare_flags |= CLONE_NEWIPC;

Just check here if unshare_flags is still 0, i.e.:

	if (unshare_flags == 0)
		goto bad_unshare_ns_out;

> +	if ((err = unshare_fs(unshare_flags, &new_fs)))
> +		goto bad_unshare_ns_out;
> +	if ((err = unshare_mnt_namespace(unshare_flags, &new_mnt, new_fs)))
> +		goto bad_unshare_ns_cleanup_fs;
> +	if ((err = unshare_utsname(unshare_flags, &new_uts)))
> +		goto bad_unshare_ns_cleanup_mnt;
> +	if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
> +		goto bad_unshare_ns_cleanup_uts;
> +
> +	if (new_mnt || new_uts || new_ipc) {
> +		old_nsproxy = current->nsproxy;
> +		new_nsproxy = dup_namespaces(old_nsproxy);
> +		if (!new_nsproxy) {
> +			err = -ENOMEM;
> +			goto bad_unshare_ns_cleanup_ipc;
> +		}
> +	}
> +
> +	if (new_fs || new_mnt || new_uts || new_ipc) {
> +
> +		task_lock(current);
> +
> +		if (new_nsproxy) {
> +			current->nsproxy = new_nsproxy;
> +			new_nsproxy = old_nsproxy;
> +		}
> +
> +		if (new_fs) {
> +			fs = current->fs;
> +			current->fs = new_fs;
> +			new_fs = fs;
> +		}
> +
> +		if (new_mnt) {
> +			mnt = current->nsproxy->mnt_ns;
> +			current->nsproxy->mnt_ns = new_mnt;
> +			new_mnt = mnt;
> +		}
> +
> +		if (new_uts) {
> +			uts = current->nsproxy->uts_ns;
> +			current->nsproxy->uts_ns = new_uts;
> +			new_uts = uts;
> +		}
> +
> +		if (new_ipc) {
> +			ipc = current->nsproxy->ipc_ns;
> +			current->nsproxy->ipc_ns = new_ipc;
> +			new_ipc = ipc;
> +		}
> +
> +		task_unlock(current);
> +	}
> +
> +	if (new_nsproxy)
> +		put_nsproxy(new_nsproxy);
> +
> +bad_unshare_ns_cleanup_ipc:
> +	if (new_ipc)
> +		put_ipc_ns(new_ipc);
> +
> +bad_unshare_ns_cleanup_uts:
> +	if (new_uts)
> +		put_uts_ns(new_uts);
> +
> +bad_unshare_ns_cleanup_mnt:
> +	if (new_mnt)
> +		put_mnt_ns(new_mnt);
> +
> +bad_unshare_ns_cleanup_fs:
> +	if (new_fs)
> +		put_fs_struct(new_fs);
> +
> +bad_unshare_ns_out:
> +	return err;
> +}
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