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Message-ID: <20220223175854.GB10272@mail.hallyn.com> Date: Wed, 23 Feb 2022 11:58:54 -0600 From: "Serge E. Hallyn" <serge@...lyn.com> To: Stefan Berger <stefanb@...ux.ibm.com> Cc: linux-integrity@...r.kernel.org, zohar@...ux.ibm.com, serge@...lyn.com, christian.brauner@...ntu.com, containers@...ts.linux.dev, dmitry.kasatkin@...il.com, ebiederm@...ssion.com, krzysztof.struczynski@...wei.com, roberto.sassu@...wei.com, mpeters@...hat.com, lhinds@...hat.com, lsturman@...hat.com, puiterwi@...hat.com, jejb@...ux.ibm.com, jamjoom@...ibm.com, linux-kernel@...r.kernel.org, paul@...l-moore.com, rgb@...hat.com, linux-security-module@...r.kernel.org, jmorris@...ei.org Subject: Re: [PATCH v10 27/27] ima: Enable IMA namespaces On Tue, Feb 01, 2022 at 03:37:35PM -0500, Stefan Berger wrote: > Introduce the IMA_NS in Kconfig for IMA namespace enablement. > > Enable the lazy initialization of an IMA namespace when a user mounts > SecurityFS and writes '1' into IMA's 'active' securityfs file. A > user_namespace will now get a pointer to an ima_namespace and therefore > implement get_current_ns() for the namespacing case that returns this > pointer. Use get_current_ns() in those places that require access to the > current IMA namespace. In some places, primarily those related to > IMA-appraisal and changes to file attributes, keep the pointer to > init_ima_ns, since there flags related to file measurements may be > affected, which are not supported in IMA namespaces, yet. > > Before using the ima_namespace pointer test it with ns_is_active() > to check whether it is NULL and whether the ima_namespace is active. > If it's not active, it cannot be used, yet. Therefore, return early > from those functions that may now get either get a NULL pointer from > this call or where ns->active is still 0. The init_ima_ns is always > set to be active, thus passing the check. > > Implement ima_ns_from_file() for SecurityFS-related files where we can > now get the IMA namespace via the user namespace pointer associated > with the superblock of the SecurityFS filesystem instance. > > Return -EACCES to IMA's securityfs files, except for the 'active' file, > until the IMA namespace has been set to active. > > Switch access to userns->ima_ns to use acquire/release semantics to ensure > that a newly created ima_namespace structure is fully visible upon access. > > Only emit the kernel log message 'policy update completed' for the > init_ima_ns. > > When parsing an IMA policy rule use the user namespace of the opener > to translate uid and gid values to kernel values rather than the user > namespace of the writer. > > Gate access to ima_appraise variable to init_ima_ns in ima_load_data() > and ima_write_policy(). > > Gate access to temp_ima_appraise variable to init_ima_ns in > ima_delete_rules(). > > Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com> > > --- > v10: > - dropped ima_ns_to_user_ns(); using current_user_ns() instead > - Pass user_namespace of file opener into ima_parse_rule and propagate > this parameter back all the way to the initial caller in the chain > - Gate access to ima_appraise to init_ima_ns in ima_write_policy() > > v9: > - ima_post_key_create_or_update: Only handle key if in init_ima_ns > - Removed ns == NULL checks where user_namespace is now passed > - Defer setting of user_ns->ima_ns until end of ima_fs_ns_init(); > required new ima_free_imans() and new user_ns_set_ima_ns() > - Only emit log message 'policy update completed' for init_ima_ns > - Introduce get_current_ns() only in this patch > - Check for ns == &init_ima_ns in ima_load_data() > --- > include/linux/ima.h | 1 + > init/Kconfig | 13 +++ > kernel/user_namespace.c | 2 + > security/integrity/ima/ima.h | 55 +++++++++++-- > security/integrity/ima/ima_appraise.c | 3 + > security/integrity/ima/ima_asymmetric_keys.c | 6 +- > security/integrity/ima/ima_fs.c | 87 ++++++++++++++++---- > security/integrity/ima/ima_init.c | 2 +- > security/integrity/ima/ima_init_ima_ns.c | 2 + > security/integrity/ima/ima_main.c | 34 +++++--- > security/integrity/ima/ima_ns.c | 15 +++- > security/integrity/ima/ima_policy.c | 43 ++++++---- > 12 files changed, 202 insertions(+), 61 deletions(-) > > diff --git a/include/linux/ima.h b/include/linux/ima.h > index c584527c0f47..a8cb2c269f61 100644 > --- a/include/linux/ima.h > +++ b/include/linux/ima.h > @@ -11,6 +11,7 @@ > #include <linux/fs.h> > #include <linux/security.h> > #include <linux/kexec.h> > +#include <linux/user_namespace.h> > #include <crypto/hash_info.h> > struct linux_binprm; > > diff --git a/init/Kconfig b/init/Kconfig > index 4b7bac10c72d..e27155e0ddba 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1247,6 +1247,19 @@ config NET_NS > Allow user space to create what appear to be multiple instances > of the network stack. > > +config IMA_NS > + bool "IMA namespace" > + depends on USER_NS > + depends on IMA > + default n > + help > + Allow the creation of an IMA namespace for each user namespace. > + Namespaced IMA enables having IMA features work separately > + in each IMA namespace. > + Currently, only the audit status flags are stored in the namespace, > + which allows the same file to be audited each time it is accessed > + in a new namespace. > + > endif # NAMESPACES > > config CHECKPOINT_RESTORE > diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c > index 6b2e3ca7ee99..653f8fa83b69 100644 > --- a/kernel/user_namespace.c > +++ b/kernel/user_namespace.c > @@ -20,6 +20,7 @@ > #include <linux/fs_struct.h> > #include <linux/bsearch.h> > #include <linux/sort.h> > +#include <linux/ima.h> > > static struct kmem_cache *user_ns_cachep __read_mostly; > static DEFINE_MUTEX(userns_state_mutex); > @@ -196,6 +197,7 @@ static void free_user_ns(struct work_struct *work) > kfree(ns->projid_map.forward); > kfree(ns->projid_map.reverse); > } > + free_ima_ns(ns); > retire_userns_sysctls(ns); > key_free_user_ns(ns); > ns_free_inum(&ns->ns); > diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h > index 05e2de7697da..73df1d8a2ece 100644 > --- a/security/integrity/ima/ima.h > +++ b/security/integrity/ima/ima.h > @@ -337,10 +337,10 @@ int ima_match_policy(struct ima_namespace *ns, > int mask, int flags, int *pcr, > struct ima_template_desc **template_desc, > const char *func_data, unsigned int *allowed_algos); > -void ima_init_policy(struct ima_namespace *ns); > +void ima_init_policy(struct user_namespace *user_ns); > void ima_update_policy(struct ima_namespace *ns); > void ima_update_policy_flags(struct ima_namespace *ns); > -ssize_t ima_parse_add_rule(struct ima_namespace *ns, char *rule); > +ssize_t ima_parse_add_rule(struct user_namespace *user_ns, char *rule); > void ima_delete_rules(struct ima_namespace *ns); > int ima_check_policy(struct ima_namespace *ns); > void ima_free_policy_rules(struct ima_namespace *ns); > @@ -538,32 +538,70 @@ struct user_namespace *ima_user_ns_from_file(const struct file *filp) > return file_inode(filp)->i_sb->s_user_ns; > } > > +#ifdef CONFIG_IMA_NS > + > static inline struct ima_namespace > *ima_ns_from_user_ns(struct user_namespace *user_ns) > { > - if (user_ns == &init_user_ns) > - return &init_ima_ns; > - return NULL; > + /* Pairs with smp_store_releases() in user_ns_set_ima_ns(). */ > + return smp_load_acquire(&user_ns->ima_ns); > } > > -#ifdef CONFIG_IMA_NS > +static inline void user_ns_set_ima_ns(struct user_namespace *user_ns, > + struct ima_namespace *ns) > +{ > + /* Pairs with smp_load_acquire() in ima_ns_from_user_ns() */ > + smp_store_release(&user_ns->ima_ns, ns); > +} > + > +static inline struct ima_namespace *get_current_ns(void) > +{ > + return ima_ns_from_user_ns(current_user_ns()); > +} > > struct ima_namespace *create_ima_ns(void); > > +void ima_free_ima_ns(struct ima_namespace *ns); > + > struct ns_status *ima_get_ns_status(struct ima_namespace *ns, > struct inode *inode, > struct integrity_iint_cache *iint); > > void ima_free_ns_status_tree(struct ima_namespace *ns); > > +static inline struct ima_namespace *ima_ns_from_file(const struct file *filp) > +{ Why is it ok here to dereference userns->ima_ns without going through ima_ns_from_user_ns() to do the smp_load_acquire()? > + return ima_user_ns_from_file(filp)->ima_ns; > +} > + > #else -serge
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