Re: [RFC PATCH v2 1/3] ima: extend clone() with IMA namespace support

[Eric W. Biederman]

Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx> writes:

> From: Yuqiong Sun <suny@xxxxxxxxxx>
>
> Add new CONFIG_IMA_NS config option.  Let clone() create a new IMA
> namespace upon CLONE_NEWNS flag. Add ima_ns data structure in nsproxy.
> ima_ns is allocated and freed upon IMA namespace creation and exit.
> Currently, the ima_ns contains no useful IMA data but only a dummy
> interface. This patch creates the framework for namespacing the different
> aspects of IMA (eg. IMA-audit, IMA-measurement, IMA-appraisal).

IMA is not path based.  The only thing that belongs to a mount
namespace are paths.  Therefore IMA is completely inappropriate to
be joint with a mount namespace.

I saw that Serge even recently mentioned that you need to take
this aspect of the changes back to the drawing board.  With my
namespace maintainer hat on I repeat that.

>From a 10,000 foot view I can already tell that this is hopeless.
So for binding IMA namspaces and CLONE_NEWNS:

Nacked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>

I am not nacking IMA namespacing just inappropriately tying ima
namespaces to mount namespaces.  These should be completely separate
entities.

Eric


> Changelog:
> * Use CLONE_NEWNS instead of a new CLONE_NEWIMA flag
> * Use existing ima.h headers
> * Move the ima_namespace.c to security/integrity/ima/ima_ns.c
> * Fix typo INFO->INO
> * Each namespace free's itself, removed recursively free'ing
>   until init_ima_ns from free_ima_ns()
> * Moved ima_init_ns and related functions into own file that is
>   always compiled
> * Fixed putting of imans->parent
> * Move IMA namespace creation from nsproxy into mount namespace
>   code
>
> Signed-off-by: Yuqiong Sun <suny@xxxxxxxxxx>
> Signed-off-by: Mehmet Kayaalp <mkayaalp@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx>
> ---
>  fs/mount.h                               | 14 -----
>  fs/namespace.c                           | 29 ++++++++--
>  include/linux/ima.h                      | 67 +++++++++++++++++++++++
>  include/linux/mount.h                    | 20 ++++++-
>  init/Kconfig                             |  8 +++
>  kernel/nsproxy.c                         |  1 +
>  security/integrity/ima/Makefile          |  3 +-
>  security/integrity/ima/ima.h             |  4 ++
>  security/integrity/ima/ima_init.c        |  4 ++
>  security/integrity/ima/ima_init_ima_ns.c | 38 +++++++++++++
>  security/integrity/ima/ima_ns.c          | 91 ++++++++++++++++++++++++++++++++
>  11 files changed, 260 insertions(+), 19 deletions(-)
>  create mode 100644 security/integrity/ima/ima_init_ima_ns.c
>  create mode 100644 security/integrity/ima/ima_ns.c
>
> diff --git a/fs/mount.h b/fs/mount.h
> index f39bc9da4d73..e19ebde97756 100644
> --- a/fs/mount.h
> +++ b/fs/mount.h
> @@ -5,20 +5,6 @@
>  #include <linux/ns_common.h>
>  #include <linux/fs_pin.h>
>  
> -struct mnt_namespace {
> -	atomic_t		count;
> -	struct ns_common	ns;
> -	struct mount *	root;
> -	struct list_head	list;
> -	struct user_namespace	*user_ns;
> -	struct ucounts		*ucounts;
> -	u64			seq;	/* Sequence number to prevent loops */
> -	wait_queue_head_t poll;
> -	u64 event;
> -	unsigned int		mounts; /* # of mounts in the namespace */
> -	unsigned int		pending_mounts;
> -} __randomize_layout;
> -
>  struct mnt_pcp {
>  	int mnt_count;
>  	int mnt_writers;
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 9d1374ab6e06..7f886c02278b 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -26,6 +26,7 @@
>  #include <linux/bootmem.h>
>  #include <linux/task_work.h>
>  #include <linux/sched/task.h>
> +#include <linux/ima.h>
>  
>  #include "pnode.h"
>  #include "internal.h"
> @@ -2858,6 +2859,7 @@ static void dec_mnt_namespaces(struct ucounts *ucounts)
>  
>  static void free_mnt_ns(struct mnt_namespace *ns)
>  {
> +	put_ima_ns(ns->ima_ns);
>  	ns_free_inum(&ns->ns);
>  	dec_mnt_namespaces(ns->ucounts);
>  	put_user_ns(ns->user_ns);
> @@ -2873,11 +2875,13 @@ static void free_mnt_ns(struct mnt_namespace *ns)
>   */
>  static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
>  
> -static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
> +static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns,
> +					  struct ima_namespace *ima_ns)
>  {
>  	struct mnt_namespace *new_ns;
>  	struct ucounts *ucounts;
>  	int ret;
> +	int err;
>  
>  	ucounts = inc_mnt_namespaces(user_ns);
>  	if (!ucounts)
> @@ -2894,6 +2898,20 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
>  		dec_mnt_namespaces(ucounts);
>  		return ERR_PTR(ret);
>  	}
> +
> +	if (ima_ns == NULL) {
> +		new_ns->ima_ns = get_ima_ns(&init_ima_ns);
> +	} else {
> +		new_ns->ima_ns = copy_ima(user_ns, ima_ns);
> +		if (IS_ERR(new_ns->ima_ns)) {
> +			err = PTR_ERR(new_ns->ima_ns);
> +			ns_free_inum(&new_ns->ns);
> +			kfree(new_ns);
> +			dec_mnt_namespaces(ucounts);
> +			return ERR_PTR(err);
> +		}
> +	}
> +
>  	new_ns->ns.ops = &mntns_operations;
>  	new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
>  	atomic_set(&new_ns->count, 1);
> @@ -2920,6 +2938,7 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
>  	int copy_flags;
>  
>  	BUG_ON(!ns);
> +	BUG_ON(!ns->ima_ns);
>  
>  	if (likely(!(flags & CLONE_NEWNS))) {
>  		get_mnt_ns(ns);
> @@ -2928,7 +2947,7 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
>  
>  	old = ns->root;
>  
> -	new_ns = alloc_mnt_ns(user_ns);
> +	new_ns = alloc_mnt_ns(user_ns, ns->ima_ns);
>  	if (IS_ERR(new_ns))
>  		return new_ns;
>  
> @@ -2989,7 +3008,8 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
>   */
>  static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
>  {
> -	struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
> +	struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns,
> +						    NULL);
>  	if (!IS_ERR(new_ns)) {
>  		struct mount *mnt = real_mount(m);
>  		mnt->mnt_ns = new_ns;
> @@ -3497,6 +3517,9 @@ static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
>  	set_fs_root(fs, &root);
>  
>  	path_put(&root);
> +
> +	imans_install(nsproxy, ns);
> +
>  	return 0;
>  }
>  
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index 0e4647e0eb60..fd150dfde277 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -12,6 +12,7 @@
>  
>  #include <linux/fs.h>
>  #include <linux/kexec.h>
> +#include <linux/mount.h>
>  struct linux_binprm;
>  
>  #ifdef CONFIG_IMA
> @@ -105,4 +106,70 @@ static inline int ima_inode_removexattr(struct dentry *dentry,
>  	return 0;
>  }
>  #endif /* CONFIG_IMA_APPRAISE */
> +
> +struct ima_namespace {
> +	struct kref kref;
> +	struct user_namespace *user_ns;
> +	struct ima_namespace *parent;
> +};
> +
> +extern struct ima_namespace init_ima_ns;
> +
> +void imans_install(struct nsproxy *nsproxy, struct ns_common *new);
> +
> +static inline struct ima_namespace *to_ima_ns(struct ns_common *ns)
> +{
> +	return container_of(ns, struct mnt_namespace, ns)->ima_ns;
> +}
> +
> +#ifdef CONFIG_IMA_NS
> +
> +void free_ima_ns(struct kref *kref);
> +
> +static inline struct ima_namespace *get_ima_ns(struct ima_namespace *ns)
> +{
> +	BUG_ON(!ns);
> +	if (ns)
> +		kref_get(&ns->kref);
> +	return ns;
> +}
> +
> +static inline void put_ima_ns(struct ima_namespace *ns)
> +{
> +	BUG_ON(!ns);
> +	if (ns)
> +		kref_put(&ns->kref, free_ima_ns);
> +}
> +
> +struct ima_namespace *copy_ima(struct user_namespace *user_ns,
> +			       struct ima_namespace *old_ns);
> +
> +static inline struct ima_namespace *get_current_ns(void)
> +{
> +	return current->nsproxy->mnt_ns->ima_ns;
> +}
> +
> +#else
> +
> +static inline struct ima_namespace *get_ima_ns(struct ima_namespace *ns)
> +{
> +	return ns;
> +}
> +
> +static inline void put_ima_ns(struct ima_namespace *ns)
> +{
> +	return;
> +}
> +
> +static inline struct ima_namespace *copy_ima(struct user_namespace *user_ns,
> +					     struct ima_namespace *old_ns)
> +{
> +	return old_ns;
> +}
> +
> +static inline struct ima_namespace *get_current_ns(void)
> +{
> +	return NULL;
> +}
> +#endif /* CONFIG_IMA_NS */
>  #endif /* _LINUX_IMA_H */
> diff --git a/include/linux/mount.h b/include/linux/mount.h
> index 45b1f56c6c2f..361c962ebd3d 100644
> --- a/include/linux/mount.h
> +++ b/include/linux/mount.h
> @@ -16,11 +16,29 @@
>  #include <linux/spinlock.h>
>  #include <linux/seqlock.h>
>  #include <linux/atomic.h>
> +#include <linux/ns_common.h>
> +#include <linux/wait.h>
>  
>  struct super_block;
>  struct vfsmount;
>  struct dentry;
> -struct mnt_namespace;
> +struct ima_namespace;
> +
> +struct mnt_namespace {
> +	atomic_t		count;
> +	struct ns_common	ns;
> +	struct mount *	root;
> +	struct list_head	list;
> +	struct user_namespace	*user_ns;
> +	struct ucounts		*ucounts;
> +	u64			seq;	/* Sequence number to prevent loops */
> +	wait_queue_head_t poll;
> +	u64 event;
> +	unsigned int		mounts; /* # of mounts in the namespace */
> +	unsigned int		pending_mounts;
> +	struct ima_namespace    *ima_ns;
> +} __randomize_layout;
> +
>  
>  #define MNT_NOSUID	0x01
>  #define MNT_NODEV	0x02
> diff --git a/init/Kconfig b/init/Kconfig
> index a9a2e2c86671..a1ad5384e081 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -931,6 +931,14 @@ config NET_NS
>  	help
>  	  Allow user space to create what appear to be multiple instances
>  	  of the network stack.
> +config IMA_NS
> +	bool "IMA namespace"
> +	depends on IMA
> +	default y
> +	help
> +	  Allow the creation of IMA namespaces for each mount namespace.
> +	  Namespaced IMA data enables having IMA features work separately
> +	  for each mount namespace.
>  
>  endif # NAMESPACES
>  
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index f6c5d330059a..7d1a35362186 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -27,6 +27,7 @@
>  #include <linux/syscalls.h>
>  #include <linux/cgroup.h>
>  #include <linux/perf_event.h>
> +#include <linux/ima.h>
>  
>  static struct kmem_cache *nsproxy_cachep;
>  
> diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
> index d921dc4f9eb0..cc60f726e651 100644
> --- a/security/integrity/ima/Makefile
> +++ b/security/integrity/ima/Makefile
> @@ -7,7 +7,8 @@
>  obj-$(CONFIG_IMA) += ima.o
>  
>  ima-y := ima_fs.o ima_queue.o ima_init.o ima_main.o ima_crypto.o ima_api.o \
> -	 ima_policy.o ima_template.o ima_template_lib.o
> +	 ima_policy.o ima_template.o ima_template_lib.o ima_init_ima_ns.o
>  ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
> +ima-$(CONFIG_IMA_NS) += ima_ns.o
>  ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
>  obj-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index d52b487ad259..e98c11c7cf75 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -291,6 +291,10 @@ static inline int ima_read_xattr(struct dentry *dentry,
>  
>  #endif /* CONFIG_IMA_APPRAISE */
>  
> +int ima_ns_init(void);
> +struct ima_namespace;
> +int ima_init_namespace(struct ima_namespace *ns);
> +
>  /* LSM based policy rules require audit */
>  #ifdef CONFIG_IMA_LSM_RULES
>  
> diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
> index 2967d497a665..7f884a71fa1c 100644
> --- a/security/integrity/ima/ima_init.c
> +++ b/security/integrity/ima/ima_init.c
> @@ -137,5 +137,9 @@ int __init ima_init(void)
>  
>  	ima_init_policy();
>  
> +	rc = ima_ns_init();
> +	if (rc != 0)
> +		return rc;
> +
>  	return ima_fs_init();
>  }
> diff --git a/security/integrity/ima/ima_init_ima_ns.c b/security/integrity/ima/ima_init_ima_ns.c
> new file mode 100644
> index 000000000000..4b081dbfac07
> --- /dev/null
> +++ b/security/integrity/ima/ima_init_ima_ns.c
> @@ -0,0 +1,38 @@
> +/*
> + * Copyright (C) 2016-2018 IBM Corporation
> + * Author: Yuqiong Sun <suny@xxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation, version 2 of the License.
> + */
> +
> +#include <linux/export.h>
> +#include <linux/user_namespace.h>
> +#include <linux/ima.h>
> +
> +int ima_init_namespace(struct ima_namespace *ns)
> +{
> +	return 0;
> +}
> +
> +int __init ima_ns_init(void)
> +{
> +	return ima_init_namespace(&init_ima_ns);
> +}
> +
> +struct ima_namespace init_ima_ns = {
> +	.kref = KREF_INIT(2),
> +	.user_ns = &init_user_ns,
> +	.parent = NULL,
> +};
> +EXPORT_SYMBOL(init_ima_ns);
> +
> +void imans_install(struct nsproxy *nsproxy, struct ns_common *new)
> +{
> +	struct ima_namespace *ns = to_ima_ns(new);
> +
> +	get_ima_ns(ns);
> +	put_ima_ns(nsproxy->mnt_ns->ima_ns);
> +	nsproxy->mnt_ns->ima_ns = ns;
> +}
> diff --git a/security/integrity/ima/ima_ns.c b/security/integrity/ima/ima_ns.c
> new file mode 100644
> index 000000000000..7ab4322c88ae
> --- /dev/null
> +++ b/security/integrity/ima/ima_ns.c
> @@ -0,0 +1,91 @@
> +/*
> + * Copyright (C) 2016-2018 IBM Corporation
> + * Author: Yuqiong Sun <suny@xxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation, version 2 of the License.
> + */
> +
> +#include <linux/user_namespace.h>
> +#include <linux/kref.h>
> +#include <linux/slab.h>
> +#include <linux/ima.h>
> +#include <linux/mount.h>
> +
> +#include "ima.h"
> +
> +static struct ima_namespace *create_ima_ns(void)
> +{
> +	struct ima_namespace *ima_ns;
> +
> +	ima_ns = kmalloc(sizeof(*ima_ns), GFP_KERNEL);
> +	if (ima_ns)
> +		kref_init(&ima_ns->kref);
> +
> +	return ima_ns;
> +}
> +
> +/**
> + * Clone a new ns copying an original ima namespace, setting refcount to 1
> + *
> + * @old_ns: old ima namespace to clone
> + * @user_ns: user namespace that current task runs in
> + * Return ERR_PTR(-ENOMEM) on error (failure to kmalloc), new ns otherwise
> + */
> +static struct ima_namespace *clone_ima_ns(struct user_namespace *user_ns,
> +					  struct ima_namespace *old_ns)
> +{
> +	struct ima_namespace *ns;
> +
> +	ns = create_ima_ns();
> +	if (!ns)
> +		return ERR_PTR(-ENOMEM);
> +
> +	get_ima_ns(old_ns);
> +	ns->parent = old_ns;
> +	ns->user_ns = get_user_ns(user_ns);
> +
> +	ima_init_namespace(ns);
> +
> +	return ns;
> +}
> +
> +/**
> + * Copy task's ima namespace, or clone it if flags specifies CLONE_NEWNS.
> + *
> + * @flags: flags used in the clone syscall
> + * @user_ns: user namespace that current task runs in
> + * @old_ns: old ima namespace to clone
> + */
> +
> +struct ima_namespace *copy_ima(struct user_namespace *user_ns,
> +			       struct ima_namespace *old_ns)
> +{
> +	struct ima_namespace *new_ns;
> +
> +	BUG_ON(!old_ns);
> +	get_ima_ns(old_ns);
> +
> +	new_ns = clone_ima_ns(user_ns, old_ns);
> +	put_ima_ns(old_ns);
> +
> +	return new_ns;
> +}
> +
> +static void destroy_ima_ns(struct ima_namespace *ns)
> +{
> +	put_user_ns(ns->user_ns);
> +	put_ima_ns(ns->parent);
> +	kfree(ns);
> +}
> +
> +void free_ima_ns(struct kref *kref)
> +{
> +	struct ima_namespace *ns;
> +
> +	ns = container_of(kref, struct ima_namespace, kref);
> +	BUG_ON(ns == &init_ima_ns);
> +
> +	destroy_ima_ns(ns);
> +}