Unverified Commit f2a8d52e authored by Christian Brauner's avatar Christian Brauner
Browse files

nsproxy: add struct nsset 



Add a simple struct nsset. It holds all necessary pieces to switch to a new
set of namespaces without leaving a task in a half-switched state which we
will make use of in the next patch. This patch switches the existing setns
logic over without causing a change in setns() behavior. This brings
setns() closer to how unshare() works(). The prepare_ns() function is
responsible to prepare all necessary information. This has two reasons.
First it minimizes dependencies between individual namespaces, i.e. all
install handler can expect that all fields are properly initialized
independent in what order they are called in. Second, this makes the code
easier to maintain and easier to follow if it needs to be changed.

The prepare_ns() helper will only be switched over to use a flags argument
in the next patch. Here it will still use nstype as a simple integer
argument which was argued would be clearer. I'm not particularly
opinionated about this if it really helps or not. The struct nsset itself
already contains the flags field since its name already indicates that it
can contain information required by different namespaces. None of this
should have functional consequences.

Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: default avatarSerge Hallyn <serge@hallyn.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Jann Horn <jannh@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Link: https://lore.kernel.org/r/20200505140432.181565-2-christian.brauner@ubuntu.com
parent 0e698dfa

fs/namespace.c

+6 −4
Original line number Original line Diff line number Diff line
@@ -3954,16 +3954,18 @@ static void mntns_put(struct ns_common *ns) 
	put_mnt_ns(to_mnt_ns(ns));

	put_mnt_ns(to_mnt_ns(ns));

}

}





static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)

static int mntns_install(struct nsset *nsset, struct ns_common *ns)

{

{

	struct fs_struct *fs = current->fs;

	struct nsproxy *nsproxy = nsset->nsproxy;

	struct fs_struct *fs = nsset->fs;

	struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;

	struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;

	struct user_namespace *user_ns = nsset->cred->user_ns;

	struct path root;

	struct path root;

	int err;

	int err;





	if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||

	if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||

	    !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||

	    !ns_capable(user_ns, CAP_SYS_CHROOT) ||

	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))

	    !ns_capable(user_ns, CAP_SYS_ADMIN))

		return -EPERM;

		return -EPERM;





	if (is_anon_ns(mnt_ns))

	if (is_anon_ns(mnt_ns))

include/linux/mnt_namespace.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -6,6 +6,7 @@ 
struct mnt_namespace;

struct mnt_namespace;

struct fs_struct;

struct fs_struct;

struct user_namespace;

struct user_namespace;

struct ns_common;





extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *,

extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *,

		struct user_namespace *, struct fs_struct *);

		struct user_namespace *, struct fs_struct *);

include/linux/nsproxy.h

+24 −0
Original line number Original line Diff line number Diff line
@@ -41,6 +41,30 @@ struct nsproxy { 
};

};

extern struct nsproxy init_nsproxy;

extern struct nsproxy init_nsproxy;





/*

 * A structure to encompass all bits needed to install

 * a partial or complete new set of namespaces.

 *

 * If a new user namespace is requested cred will

 * point to a modifiable set of credentials. If a pointer

 * to a modifiable set is needed nsset_cred() must be

 * used and tested.

 */

struct nsset {

	unsigned flags;

	struct nsproxy *nsproxy;

	struct fs_struct *fs;

	const struct cred *cred;

};



static inline struct cred *nsset_cred(struct nsset *set)

{

	if (set->flags & CLONE_NEWUSER)

		return (struct cred *)set->cred;



	return NULL;

}



/*

/*

 * the namespaces access rules are:

 * the namespaces access rules are:

 *

 *

include/linux/proc_ns.h

+2 −2
Original line number Original line Diff line number Diff line
@@ -8,7 +8,7 @@ 
#include <linux/ns_common.h>

#include <linux/ns_common.h>





struct pid_namespace;

struct pid_namespace;

struct nsproxy;

struct nsset;

struct path;

struct path;

struct task_struct;

struct task_struct;

struct inode;

struct inode;
@@ -19,7 +19,7 @@ struct proc_ns_operations { 
	int type;

	int type;

	struct ns_common *(*get)(struct task_struct *task);

	struct ns_common *(*get)(struct task_struct *task);

	void (*put)(struct ns_common *ns);

	void (*put)(struct ns_common *ns);

	int (*install)(struct nsproxy *nsproxy, struct ns_common *ns);

	int (*install)(struct nsset *nsset, struct ns_common *ns);

	struct user_namespace *(*owner)(struct ns_common *ns);

	struct user_namespace *(*owner)(struct ns_common *ns);

	struct ns_common *(*get_parent)(struct ns_common *ns);

	struct ns_common *(*get_parent)(struct ns_common *ns);

} __randomize_layout;

} __randomize_layout;

ipc/namespace.c

+3 −4
Original line number Original line Diff line number Diff line
@@ -177,15 +177,14 @@ static void ipcns_put(struct ns_common *ns) 
	return put_ipc_ns(to_ipc_ns(ns));

	return put_ipc_ns(to_ipc_ns(ns));

}

}





static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)

static int ipcns_install(struct nsset *nsset, struct ns_common *new)

{

{

	struct nsproxy *nsproxy = nsset->nsproxy;

	struct ipc_namespace *ns = to_ipc_ns(new);

	struct ipc_namespace *ns = to_ipc_ns(new);

	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||

	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||

	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))

	    !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))

		return -EPERM;

		return -EPERM;





	/* Ditch state from the old ipc namespace */

	exit_sem(current);

	put_ipc_ns(nsproxy->ipc_ns);

	put_ipc_ns(nsproxy->ipc_ns);

	nsproxy->ipc_ns = get_ipc_ns(ns);

	nsproxy->ipc_ns = get_ipc_ns(ns);

	return 0;

	return 0;

CRA Git | Maintained and supported by SUSTech CRA and CCSE