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Diffstat (limited to 'security/integrity/ima/ima_policy.c')
-rw-r--r--security/integrity/ima/ima_policy.c301
1 files changed, 269 insertions, 32 deletions
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 3997e206f82d..0a3b781f18e5 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -16,7 +16,9 @@
#include <linux/magic.h>
#include <linux/parser.h>
#include <linux/slab.h>
+#include <linux/rculist.h>
#include <linux/genhd.h>
+#include <linux/seq_file.h>
#include "ima.h"
@@ -38,6 +40,7 @@
#define AUDIT 0x0040
int ima_policy_flag;
+static int temp_ima_appraise;
#define MAX_LSM_RULES 6
enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
@@ -135,11 +138,11 @@ 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 +174,18 @@ 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 +196,6 @@ static void ima_lsm_update_rules(void)
BUG_ON(!entry->lsm[i].rule);
}
}
- mutex_unlock(&ima_rules_mutex);
}
/**
@@ -319,9 +318,9 @@ 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 +328,8 @@ 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 +351,7 @@ int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask,
if (!actmask)
break;
}
+ rcu_read_unlock();
return action;
}
@@ -365,12 +366,12 @@ 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;
}
+ ima_appraise |= temp_ima_appraise;
if (!ima_appraise)
ima_policy_flag &= ~IMA_APPRAISE;
}
@@ -415,16 +416,48 @@ void __init ima_init_policy(void)
ima_rules = &ima_default_rules;
}
+/* Make sure we have a valid policy, at least containing some rules. */
+int ima_check_policy()
+{
+ if (list_empty(&ima_temp_rules))
+ return -EINVAL;
+ return 0;
+}
+
/**
* 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();
}
@@ -436,8 +469,8 @@ enum {
Opt_obj_user, Opt_obj_role, Opt_obj_type,
Opt_subj_user, Opt_subj_role, Opt_subj_type,
Opt_func, Opt_mask, Opt_fsmagic,
- Opt_uid, Opt_euid, Opt_fowner,
- Opt_appraise_type, Opt_fsuuid, Opt_permit_directio
+ Opt_fsuuid, Opt_uid, Opt_euid, Opt_fowner,
+ Opt_appraise_type, Opt_permit_directio
};
static match_table_t policy_tokens = {
@@ -734,9 +767,9 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
if (!result && (entry->action == UNKNOWN))
result = -EINVAL;
else if (entry->func == MODULE_CHECK)
- ima_appraise |= IMA_APPRAISE_MODULES;
+ temp_ima_appraise |= IMA_APPRAISE_MODULES;
else if (entry->func == FIRMWARE_CHECK)
- ima_appraise |= IMA_APPRAISE_FIRMWARE;
+ temp_ima_appraise |= IMA_APPRAISE_FIRMWARE;
audit_log_format(ab, "res=%d", !result);
audit_log_end(ab);
return result;
@@ -746,7 +779,7 @@ 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 +815,230 @@ 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) {
+ temp_ima_appraise = 0;
+ 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);
}
+
+#ifdef CONFIG_IMA_READ_POLICY
+enum {
+ mask_exec = 0, mask_write, mask_read, mask_append
+};
+
+static char *mask_tokens[] = {
+ "MAY_EXEC",
+ "MAY_WRITE",
+ "MAY_READ",
+ "MAY_APPEND"
+};
+
+enum {
+ func_file = 0, func_mmap, func_bprm,
+ func_module, func_firmware, func_post
+};
+
+static char *func_tokens[] = {
+ "FILE_CHECK",
+ "MMAP_CHECK",
+ "BPRM_CHECK",
+ "MODULE_CHECK",
+ "FIRMWARE_CHECK",
+ "POST_SETATTR"
+};
+
+void *ima_policy_start(struct seq_file *m, loff_t *pos)
+{
+ loff_t l = *pos;
+ struct ima_rule_entry *entry;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(entry, ima_rules, list) {
+ if (!l--) {
+ rcu_read_unlock();
+ return entry;
+ }
+ }
+ rcu_read_unlock();
+ return NULL;
+}
+
+void *ima_policy_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ struct ima_rule_entry *entry = v;
+
+ rcu_read_lock();
+ entry = list_entry_rcu(entry->list.next, struct ima_rule_entry, list);
+ rcu_read_unlock();
+ (*pos)++;
+
+ return (&entry->list == ima_rules) ? NULL : entry;
+}
+
+void ima_policy_stop(struct seq_file *m, void *v)
+{
+}
+
+#define pt(token) policy_tokens[token + Opt_err].pattern
+#define mt(token) mask_tokens[token]
+#define ft(token) func_tokens[token]
+
+int ima_policy_show(struct seq_file *m, void *v)
+{
+ struct ima_rule_entry *entry = v;
+ int i = 0;
+ char tbuf[64] = {0,};
+
+ rcu_read_lock();
+
+ if (entry->action & MEASURE)
+ seq_puts(m, pt(Opt_measure));
+ if (entry->action & DONT_MEASURE)
+ seq_puts(m, pt(Opt_dont_measure));
+ if (entry->action & APPRAISE)
+ seq_puts(m, pt(Opt_appraise));
+ if (entry->action & DONT_APPRAISE)
+ seq_puts(m, pt(Opt_dont_appraise));
+ if (entry->action & AUDIT)
+ seq_puts(m, pt(Opt_audit));
+
+ seq_puts(m, " ");
+
+ if (entry->flags & IMA_FUNC) {
+ switch (entry->func) {
+ case FILE_CHECK:
+ seq_printf(m, pt(Opt_func), ft(func_file));
+ break;
+ case MMAP_CHECK:
+ seq_printf(m, pt(Opt_func), ft(func_mmap));
+ break;
+ case BPRM_CHECK:
+ seq_printf(m, pt(Opt_func), ft(func_bprm));
+ break;
+ case MODULE_CHECK:
+ seq_printf(m, pt(Opt_func), ft(func_module));
+ break;
+ case FIRMWARE_CHECK:
+ seq_printf(m, pt(Opt_func), ft(func_firmware));
+ break;
+ case POST_SETATTR:
+ seq_printf(m, pt(Opt_func), ft(func_post));
+ break;
+ default:
+ snprintf(tbuf, sizeof(tbuf), "%d", entry->func);
+ seq_printf(m, pt(Opt_func), tbuf);
+ break;
+ }
+ seq_puts(m, " ");
+ }
+
+ if (entry->flags & IMA_MASK) {
+ if (entry->mask & MAY_EXEC)
+ seq_printf(m, pt(Opt_mask), mt(mask_exec));
+ if (entry->mask & MAY_WRITE)
+ seq_printf(m, pt(Opt_mask), mt(mask_write));
+ if (entry->mask & MAY_READ)
+ seq_printf(m, pt(Opt_mask), mt(mask_read));
+ if (entry->mask & MAY_APPEND)
+ seq_printf(m, pt(Opt_mask), mt(mask_append));
+ seq_puts(m, " ");
+ }
+
+ if (entry->flags & IMA_FSMAGIC) {
+ snprintf(tbuf, sizeof(tbuf), "0x%lx", entry->fsmagic);
+ seq_printf(m, pt(Opt_fsmagic), tbuf);
+ seq_puts(m, " ");
+ }
+
+ if (entry->flags & IMA_FSUUID) {
+ seq_puts(m, "fsuuid=");
+ for (i = 0; i < ARRAY_SIZE(entry->fsuuid); ++i) {
+ switch (i) {
+ case 4:
+ case 6:
+ case 8:
+ case 10:
+ seq_puts(m, "-");
+ }
+ seq_printf(m, "%x", entry->fsuuid[i]);
+ }
+ seq_puts(m, " ");
+ }
+
+ if (entry->flags & IMA_UID) {
+ snprintf(tbuf, sizeof(tbuf), "%d", __kuid_val(entry->uid));
+ seq_printf(m, pt(Opt_uid), tbuf);
+ seq_puts(m, " ");
+ }
+
+ if (entry->flags & IMA_EUID) {
+ snprintf(tbuf, sizeof(tbuf), "%d", __kuid_val(entry->uid));
+ seq_printf(m, pt(Opt_euid), tbuf);
+ seq_puts(m, " ");
+ }
+
+ if (entry->flags & IMA_FOWNER) {
+ snprintf(tbuf, sizeof(tbuf), "%d", __kuid_val(entry->fowner));
+ seq_printf(m, pt(Opt_fowner), tbuf);
+ seq_puts(m, " ");
+ }
+
+ for (i = 0; i < MAX_LSM_RULES; i++) {
+ if (entry->lsm[i].rule) {
+ switch (i) {
+ case LSM_OBJ_USER:
+ seq_printf(m, pt(Opt_obj_user),
+ (char *)entry->lsm[i].args_p);
+ break;
+ case LSM_OBJ_ROLE:
+ seq_printf(m, pt(Opt_obj_role),
+ (char *)entry->lsm[i].args_p);
+ break;
+ case LSM_OBJ_TYPE:
+ seq_printf(m, pt(Opt_obj_type),
+ (char *)entry->lsm[i].args_p);
+ break;
+ case LSM_SUBJ_USER:
+ seq_printf(m, pt(Opt_subj_user),
+ (char *)entry->lsm[i].args_p);
+ break;
+ case LSM_SUBJ_ROLE:
+ seq_printf(m, pt(Opt_subj_role),
+ (char *)entry->lsm[i].args_p);
+ break;
+ case LSM_SUBJ_TYPE:
+ seq_printf(m, pt(Opt_subj_type),
+ (char *)entry->lsm[i].args_p);
+ break;
+ }
+ }
+ }
+ if (entry->flags & IMA_DIGSIG_REQUIRED)
+ seq_puts(m, "appraise_type=imasig ");
+ if (entry->flags & IMA_PERMIT_DIRECTIO)
+ seq_puts(m, "permit_directio ");
+ rcu_read_unlock();
+ seq_puts(m, "\n");
+ return 0;
+}
+#endif /* CONFIG_IMA_READ_POLICY */
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.