diff options
| -rw-r--r-- | security/integrity/ima/Kconfig | 11 | ||||
| -rw-r--r-- | security/integrity/ima/ima_fs.c | 13 | ||||
| -rw-r--r-- | security/integrity/ima/ima_policy.c | 79 |
3 files changed, 75 insertions, 28 deletions
diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig index aac1be1948f0..3792b0011bdb 100644 --- a/security/integrity/ima/Kconfig +++ b/security/integrity/ima/Kconfig @@ -108,6 +108,17 @@ config IMA_DEFAULT_HASH default "sha512" if IMA_DEFAULT_HASH_SHA512 default "wp512" if IMA_DEFAULT_HASH_WP512 +config IMA_WRITE_POLICY + bool "Enable multiple writes to the IMA policy" + depends on IMA + default n + help + IMA policy can now be updated multiple times. The new rules get + appended to the original policy. Have in mind that the rules are + scanned in FIFO order so be careful when you design and add new ones. + + If unsure, say N. + config IMA_APPRAISE bool "Appraise integrity measurements" depends on IMA diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c index 30aced99bc55..777867d42d27 100644 --- a/security/integrity/ima/ima_fs.c +++ b/security/integrity/ima/ima_fs.c @@ -25,6 +25,8 @@ #include "ima.h" +static DEFINE_MUTEX(ima_write_mutex); + static int valid_policy = 1; static ssize_t ima_show_htable_value(char __user *buf, size_t count, @@ -261,6 +263,11 @@ static ssize_t ima_write_policy(struct file *file, const char __user *buf, { char *data = NULL; ssize_t result; + int res; + + res = mutex_lock_interruptible(&ima_write_mutex); + if (res) + return res; if (datalen >= PAGE_SIZE) datalen = PAGE_SIZE - 1; @@ -286,6 +293,8 @@ out: if (result < 0) valid_policy = 0; kfree(data); + mutex_unlock(&ima_write_mutex); + return result; } @@ -337,8 +346,12 @@ static int ima_release_policy(struct inode *inode, struct file *file) return 0; } ima_update_policy(); +#ifndef CONFIG_IMA_WRITE_POLICY securityfs_remove(ima_policy); ima_policy = NULL; +#else + clear_bit(IMA_FS_BUSY, &ima_fs_flags); +#endif return 0; } diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index 3997e206f82d..10a0a9b9e22d 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -16,6 +16,7 @@ #include <linux/magic.h> #include <linux/parser.h> #include <linux/slab.h> +#include <linux/rculist.h> #include <linux/genhd.h> #include "ima.h" @@ -135,11 +136,11 @@ static struct ima_rule_entry default_appraise_rules[] = { static LIST_HEAD(ima_default_rules); static LIST_HEAD(ima_policy_rules); +static LIST_HEAD(ima_temp_rules); static struct list_head *ima_rules; -static DEFINE_MUTEX(ima_rules_mutex); - static int ima_policy __initdata; + static int __init default_measure_policy_setup(char *str) { if (ima_policy) @@ -171,21 +172,18 @@ static int __init default_appraise_policy_setup(char *str) __setup("ima_appraise_tcb", default_appraise_policy_setup); /* - * Although the IMA policy does not change, the LSM policy can be - * reloaded, leaving the IMA LSM based rules referring to the old, - * stale LSM policy. - * - * Update the IMA LSM based rules to reflect the reloaded LSM policy. - * We assume the rules still exist; and BUG_ON() if they don't. + * The LSM policy can be reloaded, leaving the IMA LSM based rules referring + * to the old, stale LSM policy. Update the IMA LSM based rules to reflect + * the reloaded LSM policy. We assume the rules still exist; and BUG_ON() if + * they don't. */ static void ima_lsm_update_rules(void) { - struct ima_rule_entry *entry, *tmp; + struct ima_rule_entry *entry; int result; int i; - mutex_lock(&ima_rules_mutex); - list_for_each_entry_safe(entry, tmp, &ima_policy_rules, list) { + list_for_each_entry(entry, &ima_policy_rules, list) { for (i = 0; i < MAX_LSM_RULES; i++) { if (!entry->lsm[i].rule) continue; @@ -196,7 +194,6 @@ static void ima_lsm_update_rules(void) BUG_ON(!entry->lsm[i].rule); } } - mutex_unlock(&ima_rules_mutex); } /** @@ -319,9 +316,9 @@ static int get_subaction(struct ima_rule_entry *rule, int func) * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type) * conditions. * - * (There is no need for locking when walking the policy list, - * as elements in the list are never deleted, nor does the list - * change.) + * Since the IMA policy may be updated multiple times we need to lock the + * list when walking it. Reads are many orders of magnitude more numerous + * than writes so ima_match_policy() is classical RCU candidate. */ int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask, int flags) @@ -329,7 +326,8 @@ int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask, struct ima_rule_entry *entry; int action = 0, actmask = flags | (flags << 1); - list_for_each_entry(entry, ima_rules, list) { + rcu_read_lock(); + list_for_each_entry_rcu(entry, ima_rules, list) { if (!(entry->action & actmask)) continue; @@ -351,6 +349,7 @@ int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask, if (!actmask) break; } + rcu_read_unlock(); return action; } @@ -365,7 +364,6 @@ void ima_update_policy_flag(void) { struct ima_rule_entry *entry; - ima_policy_flag = 0; list_for_each_entry(entry, ima_rules, list) { if (entry->action & IMA_DO_MASK) ima_policy_flag |= entry->action; @@ -419,12 +417,36 @@ void __init ima_init_policy(void) * ima_update_policy - update default_rules with new measure rules * * Called on file .release to update the default rules with a complete new - * policy. Once updated, the policy is locked, no additional rules can be - * added to the policy. + * policy. What we do here is to splice ima_policy_rules and ima_temp_rules so + * they make a queue. The policy may be updated multiple times and this is the + * RCU updater. + * + * Policy rules are never deleted so ima_policy_flag gets zeroed only once when + * we switch from the default policy to user defined. */ void ima_update_policy(void) { - ima_rules = &ima_policy_rules; + struct list_head *first, *last, *policy; + + /* append current policy with the new rules */ + first = (&ima_temp_rules)->next; + last = (&ima_temp_rules)->prev; + policy = &ima_policy_rules; + + synchronize_rcu(); + + last->next = policy; + rcu_assign_pointer(list_next_rcu(policy->prev), first); + first->prev = policy->prev; + policy->prev = last; + + /* prepare for the next policy rules addition */ + INIT_LIST_HEAD(&ima_temp_rules); + + if (ima_rules != policy) { + ima_policy_flag = 0; + ima_rules = policy; + } ima_update_policy_flag(); } @@ -746,7 +768,7 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) * ima_parse_add_rule - add a rule to ima_policy_rules * @rule - ima measurement policy rule * - * Uses a mutex to protect the policy list from multiple concurrent writers. + * Avoid locking by allowing just one writer at a time in ima_write_policy() * Returns the length of the rule parsed, an error code on failure */ ssize_t ima_parse_add_rule(char *rule) @@ -782,26 +804,27 @@ ssize_t ima_parse_add_rule(char *rule) return result; } - mutex_lock(&ima_rules_mutex); - list_add_tail(&entry->list, &ima_policy_rules); - mutex_unlock(&ima_rules_mutex); + list_add_tail(&entry->list, &ima_temp_rules); return len; } -/* ima_delete_rules called to cleanup invalid policy */ +/** + * ima_delete_rules() called to cleanup invalid in-flight policy. + * We don't need locking as we operate on the temp list, which is + * different from the active one. There is also only one user of + * ima_delete_rules() at a time. + */ void ima_delete_rules(void) { struct ima_rule_entry *entry, *tmp; int i; - mutex_lock(&ima_rules_mutex); - list_for_each_entry_safe(entry, tmp, &ima_policy_rules, list) { + list_for_each_entry_safe(entry, tmp, &ima_temp_rules, list) { for (i = 0; i < MAX_LSM_RULES; i++) kfree(entry->lsm[i].args_p); list_del(&entry->list); kfree(entry); } - mutex_unlock(&ima_rules_mutex); } |