From: Mehmet Kayaalp <mkayaalp@xxxxxxxxxxxxxxxxxx> Add an rbtree to the IMA namespace structure that stores a namespaced version of iint->flags in ns_status struct. Similar to the integrity_iint_cache, both the iint and ns_status are looked up using the inode pointer value. The lookup, allocate, and insertion code is also similar. In subsequent patches we will have to find all ns_status entries an iint is being used in and reset flags there. To do this, connect a list of ns_status to the integrity_iint_cache and provide a reader-writer lock in the integrity_iint_cache to lock access to the list. To simplify the code in the non-namespaces case embed an ns_status in the integrity_iint_cache and have it linked into the iint's ns_status list when calling ima_get_ns_status(). When getting an ns_status first try to find it in the RB tree. Here we can run into the situation that an ns_status found in the RB tree has a different iint associated with it for the same inode. In this case we need to delete the ns_status structure and get a new one. There are two cases for freeing: - when the iint is freed (inode deletion): Walk the list of ns_status entries and disconnect each ns_status from the list; take the writer lock to protect access to the list; also, take the item off the per-namespace rbtree - when the ima_namepace is freed: While walking the rbtree, remove the ns_status from the list while also holding the iint's writer lock; to be able to grab the lock we have to have a pointer to the iint on the ns_status structure. To avoid an ns_status to be freed by the two cases concurrently, prevent these two cases to run concurrently. Therefore, groups of threads deleting either inodes or ima_namespaces are allowed to run concurrently but no two threads may run and one delete an inode and the other an ima_namespace. Signed-off-by: Mehmet Kayaalp <mkayaalp@xxxxxxxxxxxxxxxxxx> Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx> --- Design discussion: - https://lore.kernel.org/linux-integrity/20220201203735.164593-1-stefanb@xxxxxxxxxxxxx/T/#m500a621141c52dc0e34cf11ba37b4032a2de84fd v9: - Move ns_status into integrity.h and embedded it into integrity_iint_cache for the non-CONFIG_IMA_NS case --- include/linux/ima.h | 7 + security/integrity/iint.c | 7 + security/integrity/ima/Makefile | 2 +- security/integrity/ima/ima.h | 18 ++ security/integrity/ima/ima_init_ima_ns.c | 5 + security/integrity/ima/ima_ns.c | 1 + security/integrity/ima/ima_ns_status.c | 344 +++++++++++++++++++++++ security/integrity/integrity.h | 35 ++- 8 files changed, 417 insertions(+), 2 deletions(-) create mode 100644 security/integrity/ima/ima_ns_status.c diff --git a/include/linux/ima.h b/include/linux/ima.h index a1216a3ad9ad..024908ad4eaa 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -230,12 +230,19 @@ static inline bool ima_appraise_signature(enum kernel_read_file_id func) void free_ima_ns(struct user_namespace *ns); +void ima_free_ns_status_list(struct list_head *head, rwlock_t *ns_list_lock); + #else static inline void free_ima_ns(struct user_namespace *user_ns) { } +static inline void ima_free_ns_status_list(struct list_head *head, + rwlock_t *ns_list_lock) +{ +} + #endif /* CONFIG_IMA_NS */ #endif /* _LINUX_IMA_H */ diff --git a/security/integrity/iint.c b/security/integrity/iint.c index 8638976f7990..371cbceaf479 100644 --- a/security/integrity/iint.c +++ b/security/integrity/iint.c @@ -19,6 +19,7 @@ #include <linux/uaccess.h> #include <linux/security.h> #include <linux/lsm_hooks.h> +#include <linux/ima.h> #include "integrity.h" static struct rb_root integrity_iint_tree = RB_ROOT; @@ -82,6 +83,8 @@ static void iint_free(struct integrity_iint_cache *iint) iint->ima_creds_status = INTEGRITY_UNKNOWN; iint->evm_status = INTEGRITY_UNKNOWN; iint->measured_pcrs = 0; + rwlock_init(&iint->ns_list_lock); + INIT_LIST_HEAD(&iint->ns_list); kmem_cache_free(iint_cache, iint); } @@ -155,6 +158,8 @@ void integrity_inode_free(struct inode *inode) rb_erase(&iint->rb_node, &integrity_iint_tree); write_unlock(&integrity_iint_lock); + ima_free_ns_status_list(&iint->ns_list, &iint->ns_list_lock); + iint_free(iint); } @@ -170,6 +175,8 @@ static void init_once(void *foo) iint->ima_creds_status = INTEGRITY_UNKNOWN; iint->evm_status = INTEGRITY_UNKNOWN; mutex_init(&iint->mutex); + rwlock_init(&iint->ns_list_lock); + INIT_LIST_HEAD(&iint->ns_list); } static int __init integrity_iintcache_init(void) diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile index b86a35fbed60..edfb0c30a063 100644 --- a/security/integrity/ima/Makefile +++ b/security/integrity/ima/Makefile @@ -14,7 +14,7 @@ ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o ima-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o ima-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o ima-$(CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS) += ima_queue_keys.o -ima-$(CONFIG_IMA_NS) += ima_ns.o +ima-$(CONFIG_IMA_NS) += ima_ns.o ima_ns_status.o ifeq ($(CONFIG_EFI),y) ima-$(CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT) += ima_efi.o diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index b4e1170bc170..1e2bee7387a4 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -127,6 +127,10 @@ struct ima_namespace { /* Bit numbers for above flags; use BIT() to get flag */ #define IMA_NS_LSM_UPDATE_RULES 0 + struct rb_root ns_status_tree; + rwlock_t ns_tree_lock; + struct kmem_cache *ns_status_cache; + /* policy rules */ struct list_head ima_default_rules; /* Kconfig, builtin & arch rules */ struct list_head ima_policy_rules; /* arch & custom rules */ @@ -511,6 +515,12 @@ static inline struct ima_namespace struct ima_namespace *create_ima_ns(void); +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); + #else static inline struct ima_namespace *create_ima_ns(void) @@ -519,6 +529,14 @@ static inline struct ima_namespace *create_ima_ns(void) return ERR_PTR(-EFAULT); } +static inline struct ns_status *ima_get_ns_status + (struct ima_namespace *ns, + struct inode *inode, + struct integrity_iint_cache *iint) +{ + return NULL; +} + #endif /* CONFIG_IMA_NS */ #endif /* __LINUX_IMA_H */ diff --git a/security/integrity/ima/ima_init_ima_ns.c b/security/integrity/ima/ima_init_ima_ns.c index b497062090cf..41e7db0c9749 100644 --- a/security/integrity/ima/ima_init_ima_ns.c +++ b/security/integrity/ima/ima_init_ima_ns.c @@ -12,6 +12,11 @@ int ima_init_namespace(struct ima_namespace *ns) { int ret; + ns->ns_status_tree = RB_ROOT; + rwlock_init(&ns->ns_tree_lock); + /* Use KMEM_CACHE for simplicity */ + ns->ns_status_cache = KMEM_CACHE(ns_status, SLAB_PANIC); + INIT_LIST_HEAD(&ns->ima_default_rules); INIT_LIST_HEAD(&ns->ima_policy_rules); INIT_LIST_HEAD(&ns->ima_temp_rules); diff --git a/security/integrity/ima/ima_ns.c b/security/integrity/ima/ima_ns.c index b3b81a1e313e..29af6fea2d74 100644 --- a/security/integrity/ima/ima_ns.c +++ b/security/integrity/ima/ima_ns.c @@ -29,6 +29,7 @@ static void destroy_ima_ns(struct ima_namespace *ns) unregister_blocking_lsm_notifier(&ns->ima_lsm_policy_notifier); kfree(ns->arch_policy_entry); ima_free_policy_rules(ns); + ima_free_ns_status_tree(ns); } void free_ima_ns(struct user_namespace *user_ns) diff --git a/security/integrity/ima/ima_ns_status.c b/security/integrity/ima/ima_ns_status.c new file mode 100644 index 000000000000..9c753caad6ac --- /dev/null +++ b/security/integrity/ima/ima_ns_status.c @@ -0,0 +1,344 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2016-2021 IBM Corporation + * Author: + * Yuqiong Sun <suny@xxxxxxxxxx> + * Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx> + */ + +#include <linux/user_namespace.h> +#include <linux/ima.h> + +#include "ima.h" + +/* + * An ns_status must be on a per-namespace rbtree and on a per-iint list. + * + * Locking order for ns_status: + * 1) ns->ns_tree_lock : Lock the rbtree + * 2) iint->ns_list_lock: Lock the list + * + * An ns_status can be freed either by walking the rbtree (namespace deletion) + * or by walking the linked list of ns_status (inode/iint deletion). There are + * two functions that implement each one of the cases. To avoid concurrent + * freeing of the same ns_status, the two freeing paths cannot be run + * concurrently but each path can be run by multiple threads since no two + * threads will free the same inode/iint and no two threads will free the same + * namespace. Grouping threads like this ensures that: + * - while walking the rbtree: all ns_status will be on their list and the iint + * will still exist + * - while walking the list: all ns_status will be on their rbtree + */ +enum lk_group { + GRP_NS_STATUS_LIST = 0, + GRP_NS_STATUS_TREE +}; + +static atomic_t lg_ctr[2] = { + ATOMIC_INIT(0), + ATOMIC_INIT(0) +}; + +static DEFINE_SPINLOCK(lg_ctr_lock); + +static struct wait_queue_head lg_wq[2] = { + __WAIT_QUEUE_HEAD_INITIALIZER(lg_wq[0]), + __WAIT_QUEUE_HEAD_INITIALIZER(lg_wq[1]) +}; + +static atomic_t ns_list_waiters = ATOMIC_INIT(0); + +/* + * Any number of concurrent threads may free ns_status's in either one of the + * groups but the groups must not run concurrently. The GRP_NS_STATUS_TREE + * group yields to waiters in the GRP_NS_STATUS_LIST group since namespace + * deletion has more time. + */ +static void lock_group(enum lk_group group) +{ + unsigned long flags; + bool done = false; + int announced = 0; + + while (1) { + spin_lock_irqsave(&lg_ctr_lock, flags); + + switch (group) { + case GRP_NS_STATUS_LIST: + if (atomic_read(&lg_ctr[GRP_NS_STATUS_TREE]) == 0) { + if (announced) + atomic_dec(&ns_list_waiters); + done = true; + atomic_inc(&lg_ctr[GRP_NS_STATUS_LIST]); + } else { + /* rbtree being deleted; announce waiting */ + if (!announced) { + atomic_inc(&ns_list_waiters); + announced = 1; + } + } + break; + case GRP_NS_STATUS_TREE: + if (atomic_read(&lg_ctr[GRP_NS_STATUS_LIST]) == 0 && + atomic_read(&ns_list_waiters) == 0) { + done = true; + atomic_inc(&lg_ctr[GRP_NS_STATUS_TREE]); + } + break; + } + + spin_unlock_irqrestore(&lg_ctr_lock, flags); + + if (done) + break; + + /* wait until opposite group is done */ + switch (group) { + case GRP_NS_STATUS_LIST: + wait_event_interruptible + (lg_wq[GRP_NS_STATUS_LIST], + atomic_read(&lg_ctr[GRP_NS_STATUS_TREE]) == 0); + break; + case GRP_NS_STATUS_TREE: + wait_event_interruptible + (lg_wq[GRP_NS_STATUS_TREE], + atomic_read(&lg_ctr[GRP_NS_STATUS_LIST]) == 0 && + atomic_read(&ns_list_waiters) == 0); + break; + } + } +} + +static void unlock_group(enum lk_group group) +{ + switch (group) { + case GRP_NS_STATUS_LIST: + if (atomic_dec_and_test(&lg_ctr[GRP_NS_STATUS_LIST])) + wake_up_interruptible_all(&lg_wq[GRP_NS_STATUS_TREE]); + break; + case GRP_NS_STATUS_TREE: + if (atomic_dec_and_test(&lg_ctr[GRP_NS_STATUS_TREE])) + wake_up_interruptible_all(&lg_wq[GRP_NS_STATUS_LIST]); + break; + } +} + +static void ns_status_free(struct ima_namespace *ns, + struct ns_status *ns_status) +{ + pr_debug("FREE ns_status: %p\n", ns_status); + + kmem_cache_free(ns->ns_status_cache, ns_status); +} + +/* + * ima_free_ns_status_tree - free all items on the ns_status_tree and take each + * one off the list; yield to ns_list free'ers + * + * This function is called when an ima_namespace is freed. All entries in the + * rbtree will be taken off their list and collected in a garbage collection + * list and freed at the end. This allows to walk the rbtree again. + */ +void ima_free_ns_status_tree(struct ima_namespace *ns) +{ + struct ns_status *ns_status, *next; + struct llist_node *node; + LLIST_HEAD(garbage); + unsigned int ctr; + bool restart; + + do { + ctr = 0; + restart = false; + + lock_group(GRP_NS_STATUS_TREE); + write_lock(&ns->ns_tree_lock); + + rbtree_postorder_for_each_entry_safe(ns_status, next, + &ns->ns_status_tree, + rb_node) { + write_lock(&ns_status->iint->ns_list_lock); + if (!list_empty(&ns_status->ns_next)) { + list_del_init(&ns_status->ns_next); + llist_add(&ns_status->gc_llist, &garbage); + ctr++; + } + write_unlock(&ns_status->iint->ns_list_lock); + + /* + * After some progress yield to any waiting ns_list + * free'ers. + */ + if (atomic_read(&ns_list_waiters) > 0 && ctr >= 5) { + restart = true; + break; + } + } + + write_unlock(&ns->ns_tree_lock); + unlock_group(GRP_NS_STATUS_TREE); + } while (restart); + + node = llist_del_all(&garbage); + llist_for_each_entry_safe(ns_status, next, node, gc_llist) + ns_status_free(ns, ns_status); + + kmem_cache_destroy(ns->ns_status_cache); +} + +/* + * ima_free_ns_status_list: free the list of ns_status items and take + * each one off its namespace rbtree + */ +void ima_free_ns_status_list(struct list_head *head, rwlock_t *ns_list_lock) +{ + struct ns_status *ns_status; + + lock_group(GRP_NS_STATUS_LIST); + + while (1) { + write_lock(ns_list_lock); + ns_status = list_first_entry_or_null(head, struct ns_status, + ns_next); + if (ns_status) + list_del_init(&ns_status->ns_next); + write_unlock(ns_list_lock); + + if (!ns_status) + break; + + write_lock(&ns_status->ns->ns_tree_lock); + + rb_erase(&ns_status->rb_node, &ns_status->ns->ns_status_tree); + RB_CLEAR_NODE(&ns_status->rb_node); + + write_unlock(&ns_status->ns->ns_tree_lock); + + ns_status_free(ns_status->ns, ns_status); + } + + unlock_group(GRP_NS_STATUS_LIST); +} + +/* + * ns_status_find - return the ns_status associated with an inode; + * caller must hold lock for tree + */ +static struct ns_status *ns_status_find(struct ima_namespace *ns, + struct inode *inode) +{ + struct ns_status *ns_status; + struct rb_node *n = ns->ns_status_tree.rb_node; + + while (n) { + ns_status = rb_entry(n, struct ns_status, rb_node); + + if (inode < ns_status->inode) + n = n->rb_left; + else if (inode > ns_status->inode) + n = n->rb_right; + else + break; + } + if (!n) + return NULL; + + return ns_status; +} + +static void insert_ns_status(struct ima_namespace *ns, struct inode *inode, + struct ns_status *ns_status) +{ + struct rb_node **p; + struct rb_node *node, *parent = NULL; + struct ns_status *test_status; + + p = &ns->ns_status_tree.rb_node; + while (*p) { + parent = *p; + test_status = rb_entry(parent, struct ns_status, rb_node); + if (inode < test_status->inode) + p = &(*p)->rb_left; + else + p = &(*p)->rb_right; + } + node = &ns_status->rb_node; + rb_link_node(node, parent, p); + rb_insert_color(node, &ns->ns_status_tree); +} + +static void ns_status_unlink(struct ima_namespace *ns, + struct ns_status *ns_status) +{ + write_lock(&ns_status->iint->ns_list_lock); + if (!list_empty(&ns_status->ns_next)) + list_del_init(&ns_status->ns_next); + write_unlock(&ns_status->iint->ns_list_lock); + + rb_erase(&ns_status->rb_node, &ns->ns_status_tree); + RB_CLEAR_NODE(&ns_status->rb_node); +} + +struct ns_status *ima_get_ns_status(struct ima_namespace *ns, + struct inode *inode, + struct integrity_iint_cache *iint) +{ + struct ns_status *ns_status; + bool get_new = true; + + /* + * Prevent finding the status via the list (inode/iint deletion) since + * we may free it. + */ + lock_group(GRP_NS_STATUS_TREE); + + write_lock(&ns->ns_tree_lock); + + ns_status = ns_status_find(ns, inode); + if (ns_status) { + if (unlikely(ns_status->iint != iint)) { + /* Same inode but stale iint: free it and get new */ + ns_status_unlink(ns, ns_status); + ns_status_free(ns, ns_status); + } else if (inode->i_ino == ns_status->i_ino && + inode->i_generation == ns_status->i_generation) { + goto unlock; + } else { + /* Reuse of ns_status is possible but need reset */ + ns_status_reset(ns_status); + get_new = false; + } + } + + if (get_new) { + ns_status = kmem_cache_alloc(ns->ns_status_cache, GFP_NOFS); + if (!ns_status) { + ns_status = ERR_PTR(-ENOMEM); + goto unlock; + } + + pr_debug("NEW ns_status: %p\n", ns_status); + + ns_status_init(ns_status); + insert_ns_status(ns, inode, ns_status); + } + + ns_status->iint = iint; + ns_status->inode = inode; + ns_status->ns = ns; + ns_status->i_ino = inode->i_ino; + ns_status->i_generation = inode->i_generation; + + /* make visible on list */ + write_lock(&iint->ns_list_lock); + if (list_empty(&ns_status->ns_next)) + list_add_tail(&ns_status->ns_next, &iint->ns_list); + write_unlock(&iint->ns_list_lock); + +unlock: + write_unlock(&ns->ns_tree_lock); + + unlock_group(GRP_NS_STATUS_TREE); + + return ns_status; +} diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h index 7167a6e99bdc..112836d9b33a 100644 --- a/security/integrity/integrity.h +++ b/security/integrity/integrity.h @@ -155,13 +155,39 @@ struct ima_file_id { __u8 hash[HASH_MAX_DIGESTSIZE]; } __packed; +/* integrity status of an inode in a namespace */ +struct ns_status { + struct list_head ns_next; + unsigned long flags; /* flags split with iint */ +#ifdef CONFIG_IMA_NS + struct rb_node rb_node; + struct integrity_iint_cache *iint; + struct inode *inode; + struct ima_namespace *ns; + ino_t i_ino; + u32 i_generation; + struct llist_node gc_llist; /* used while freeing */ +#endif +}; + +static inline void ns_status_reset(struct ns_status *ns_status) +{ + ns_status->flags = 0; +} + +static inline void ns_status_init(struct ns_status *ns_status) +{ + INIT_LIST_HEAD(&ns_status->ns_next); + ns_status_reset(ns_status); +} + /* integrity data associated with an inode */ struct integrity_iint_cache { struct rb_node rb_node; /* rooted in integrity_iint_tree */ struct mutex mutex; /* protects: version, flags, digest */ struct inode *inode; /* back pointer to inode in question */ u64 version; /* track inode changes */ - unsigned long flags; + unsigned long flags; /* flags split with ns_status */ unsigned long measured_pcrs; unsigned long atomic_flags; enum integrity_status ima_file_status:4; @@ -171,6 +197,13 @@ struct integrity_iint_cache { enum integrity_status ima_creds_status:4; enum integrity_status evm_status:4; struct ima_digest_data *ima_hash; + + /* + * Lock and list of ns_status for files shared by different + * namespaces + */ + rwlock_t ns_list_lock; + struct list_head ns_list; }; /* rbtree tree calls to lookup, insert, delete -- 2.36.1
