[RFC v2 2/3] LSM: Add statistics about the invocation of dynamic hooks
Sargun Dhillon
sargun at sargun.me
Fri Dec 8 04:24:12 UTC 2017
This patch builds on the dynamic hooks patch. With dynamic hooks,
/sys/kernel/security/lsm doesn't really make a lot of sense, because
the administrator is more likely interested in the per-hook modules.
There is now a /sys/kernel/security/dynamic_hooks/${HOOK_NAME} which
has the currently attached LSMs for that given hook.
Not only does it list which LSMs are hooked into each dynamic hook,
but it also lists the global accept / deny count, as well as the
per-hook accept / deny count. The earlier is useful to keep consistent
statistics across the attachment, and unattachment of LSMs.
The purpose of this is similar to the purpose of something like
iptables -L -n. With the proliferation of LSMs, it's going to
be more important to have a way to understand what's going on.
Signed-off-by: Sargun Dhillon <sargun at sargun.me>
---
include/linux/lsm_hooks.h | 4 ++
security/Kconfig | 7 +++
security/Makefile | 1 +
security/dynamic.c | 26 ++++++++++-
security/dynamic.h | 14 ++++++
security/dynamicfs.c | 109 ++++++++++++++++++++++++++++++++++++++++++++++
security/inode.c | 2 +
security/security.c | 21 +++++++--
8 files changed, 179 insertions(+), 5 deletions(-)
create mode 100644 security/dynamicfs.c
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 9c44300fc1f8..0aa9f7616f77 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -29,6 +29,8 @@
#include <linux/init.h>
#include <linux/rculist.h>
#include <linux/module.h>
+#include <linux/percpu_counter.h>
+#include <linux/percpu.h>
/**
* union security_list_options - Linux Security Module hook function list
@@ -2212,6 +2214,8 @@ enum dynamic_security_hook_type {
};
struct dynamic_security_hook {
+ struct percpu_counter invocation;
+ struct percpu_counter deny;
struct list_head list;
union security_list_options hook;
enum dynamic_security_hook_type type;
diff --git a/security/Kconfig b/security/Kconfig
index 77841bdb5bc5..d6c579d6099f 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -94,6 +94,13 @@ config SECURITY_DYNAMIC_HOOKS
They cannot circumvent the built-in LSMs.
If you are unsure how to answer this question, answer N.
+config SECURITY_DYNAMIC_HOOKS_FS
+ bool
+ default y if SECURITY_DYNAMIC_HOOKS && SECURITYFS
+ depends on SECURITY_DYNAMIC_HOOKS && SECURITYFS
+ help
+ This option enables listing of dynamically loaded LSM hooks.
+
config INTEL_TXT
bool "Enable Intel(R) Trusted Execution Technology (Intel(R) TXT)"
depends on HAVE_INTEL_TXT
diff --git a/security/Makefile b/security/Makefile
index 59e695a7e4b6..51cbec0fa49e 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_MMU) += min_addr.o
obj-$(CONFIG_SECURITY) += security.o
obj-$(CONFIG_SECURITYFS) += inode.o
obj-$(CONFIG_SECURITY_DYNAMIC_HOOKS) += dynamic.o
+obj-$(CONFIG_SECURITY_DYNAMIC_HOOKS_FS) += dynamicfs.o
obj-$(CONFIG_SECURITY_SELINUX) += selinux/
obj-$(CONFIG_SECURITY_SMACK) += smack/
obj-$(CONFIG_AUDIT) += lsm_audit.o
diff --git a/security/dynamic.c b/security/dynamic.c
index cc2f5d232e9a..d96a50a93bad 100644
--- a/security/dynamic.c
+++ b/security/dynamic.c
@@ -250,7 +250,17 @@ struct dynamic_hook dynamic_hooks[__MAX_DYNAMIC_SECURITY_HOOK] = {
*/
int security_add_dynamic_hook(struct dynamic_security_hook *hook)
{
+ int ret;
+
WARN_ON(!try_module_get(hook->owner));
+ ret = percpu_counter_init(&hook->invocation, 0, GFP_KERNEL);
+ if (ret)
+ return ret;
+ ret = percpu_counter_init(&hook->deny, 0, GFP_KERNEL);
+ if (ret) {
+ percpu_counter_destroy(&hook->invocation);
+ return ret;
+ }
mutex_lock(&dynamic_hook_lock);
list_add_tail_rcu(&hook->list, &dynamic_hooks[hook->type].head);
mutex_unlock(&dynamic_hook_lock);
@@ -262,8 +272,20 @@ EXPORT_SYMBOL_GPL(security_add_dynamic_hook);
void __init security_init_dynamic_hooks(void)
{
- int i;
+ int i, ret;
- for (i = 0; i < ARRAY_SIZE(dynamic_hooks); i++)
+ for (i = 0; i < ARRAY_SIZE(dynamic_hooks); i++) {
INIT_LIST_HEAD(&dynamic_hooks[i].head);
+ ret = percpu_counter_init(&dynamic_hooks[i].invocation, 0,
+ GFP_KERNEL);
+ if (ret)
+ panic("%s - %d - Cannot init invocation counter.\n",
+ __func__, ret);
+ ret = percpu_counter_init(&dynamic_hooks[i].deny, 0,
+ GFP_KERNEL);
+ if (ret)
+ panic("%s - %d - Cannot init deny counter.\n",
+ __func__, ret);
+
+ }
}
diff --git a/security/dynamic.h b/security/dynamic.h
index 575bc4e3d370..402cfc3f3ea3 100644
--- a/security/dynamic.h
+++ b/security/dynamic.h
@@ -2,12 +2,20 @@
#include <linux/srcu.h>
#include <linux/list.h>
#include <linux/jump_label.h>
+#include <linux/percpu_counter.h>
+#include <linux/percpu.h>
+#include <linux/fs.h>
#ifdef CONFIG_SECURITY_DYNAMIC_HOOKS
extern struct static_key_false dynamic_hooks_keys[];
struct dynamic_hook {
+ struct percpu_counter invocation;
+ struct percpu_counter deny;
const char *name;
+#ifdef CONFIG_SECURITY_DYNAMIC_HOOKS_FS
+ struct dentry *dentry;
+#endif
struct list_head head;
};
@@ -16,3 +24,9 @@ extern void security_init_dynamic_hooks(void);
#else
static void security_init_dynamic_hooks(void) {}
#endif
+
+#ifdef CONFIG_SECURITY_DYNAMIC_HOOKS_FS
+extern void securityfs_init_dynamic_hooks(void);
+#else
+static void securityfs_init_dynamic_hooks(void) {}
+#endif
diff --git a/security/dynamicfs.c b/security/dynamicfs.c
new file mode 100644
index 000000000000..d7079f0acd1c
--- /dev/null
+++ b/security/dynamicfs.c
@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/seq_file.h>
+#include <linux/percpu_counter.h>
+#include <linux/percpu.h>
+#include "dynamic.h"
+
+struct seq_private_data {
+ struct dynamic_hook *dh;
+};
+
+static void *dynamic_hooks_sop_start(struct seq_file *s, loff_t *pos)
+{
+ struct seq_private_data *pd = s->private;
+
+ return seq_list_start_head(&pd->dh->head, *pos);
+}
+
+static void *dynamic_hooks_sop_next(struct seq_file *s, void *v, loff_t *pos)
+{
+ struct seq_private_data *pd = s->private;
+
+ return seq_list_next(v, &pd->dh->head, pos);
+}
+
+static int dynamic_hooks_sop_show(struct seq_file *s, void *v)
+{
+ struct seq_private_data *pd = s->private;
+ struct dynamic_security_hook *dsh;
+
+ if (v == (void *)&pd->dh->head) {
+ seq_puts(s, "name\tinvocations\tdenies\n");
+ seq_printf(s, "all\t%lld\t%lld\n",
+ percpu_counter_sum(&pd->dh->invocation),
+ percpu_counter_sum(&pd->dh->deny));
+ return 0;
+ }
+
+ dsh = list_entry(v, typeof(*dsh), list);
+ seq_printf(s, "%s\t%lld\t%lld\n", dsh->lsm,
+ percpu_counter_sum(&dsh->invocation),
+ percpu_counter_sum(&dsh->deny));
+
+ return 0;
+}
+
+static void dynamic_hooks_sop_stop(struct seq_file *s, void *v) { }
+
+static const struct seq_operations dynamic_hooks_sops = {
+ .start = dynamic_hooks_sop_start,
+ .next = dynamic_hooks_sop_next,
+ .show = dynamic_hooks_sop_show,
+ .stop = dynamic_hooks_sop_stop,
+};
+
+static int security_dynamic_hook_open(struct inode *inode, struct file *file)
+{
+ struct seq_private_data *pd;
+
+ pd = (struct seq_private_data *)__seq_open_private(file,
+ &dynamic_hooks_sops,
+ sizeof(*pd));
+
+ if (!pd)
+ return -ENOMEM;
+
+ pd->dh = inode->i_private;
+
+ return 0;
+}
+
+static const struct file_operations dynamic_hooks_fops = {
+ .open = security_dynamic_hook_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static struct dentry *dynamic_hooks_dir;
+void securityfs_init_dynamic_hooks(void)
+{
+ struct dynamic_hook *dh;
+ int i;
+
+ dynamic_hooks_dir = securityfs_create_dir("dynamic_hooks", NULL);
+ if (IS_ERR(dynamic_hooks_dir)) {
+ pr_err("Unable to create dynamic hooks LSM directory - %ld\n",
+ PTR_ERR(dynamic_hooks_dir));
+ return;
+ }
+
+ for (i = 0; i < __MAX_DYNAMIC_SECURITY_HOOK; i++) {
+
+ dh = &dynamic_hooks[i];
+ dh->dentry = securityfs_create_file(dh->name, 0444,
+ dynamic_hooks_dir, dh,
+ &dynamic_hooks_fops);
+ if (IS_ERR(dh->dentry))
+ goto err;
+ }
+ return;
+
+err:
+ pr_err("Unable to create dynamic hook directory - %s - %ld\n",
+ dh->name, PTR_ERR(dh->dentry));
+}
diff --git a/security/inode.c b/security/inode.c
index 8dd9ca8848e4..0862be12a340 100644
--- a/security/inode.c
+++ b/security/inode.c
@@ -22,6 +22,7 @@
#include <linux/security.h>
#include <linux/lsm_hooks.h>
#include <linux/magic.h>
+#include "dynamic.h"
static struct vfsmount *mount;
static int mount_count;
@@ -335,6 +336,7 @@ static int __init securityfs_init(void)
sysfs_remove_mount_point(kernel_kobj, "security");
return retval;
}
+ securityfs_init_dynamic_hooks();
#ifdef CONFIG_SECURITY
lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
&lsm_ops);
diff --git a/security/security.c b/security/security.c
index 278f46ac8fc3..efb9bdd42ece 100644
--- a/security/security.c
+++ b/security/security.c
@@ -213,8 +213,11 @@ static_branch_unlikely(&dynamic_hooks_keys[DYNAMIC_SECURITY_HOOK_##FUNC])
struct dynamic_security_hook *dsh; \
struct dynamic_hook *dh; \
dh = &dynamic_hooks[DYNAMIC_SECURITY_HOOK_##FUNC]; \
- list_for_each_entry_rcu(dsh, &dh->head, list) \
+ percpu_counter_inc(&dh->invocation); \
+ list_for_each_entry_rcu(dsh, &dh->head, list) { \
+ percpu_counter_inc(&dsh->invocation); \
dsh->hook.FUNC(__VA_ARGS__); \
+ } \
})
#define call_void_hook(FUNC, ...) \
@@ -244,10 +247,15 @@ static_branch_unlikely(&dynamic_hooks_keys[DYNAMIC_SECURITY_HOOK_##FUNC])
if (!continue_iteration) \
break; \
dh = &dynamic_hooks[DYNAMIC_SECURITY_HOOK_##FUNC]; \
+ percpu_counter_inc(&dh->invocation); \
list_for_each_entry(dsh, &dh->head, list) { \
+ percpu_counter_inc(&dsh->invocation); \
RC = dsh->hook.FUNC(__VA_ARGS__); \
- if (RC != 0) \
+ if (RC != 0) { \
+ percpu_counter_inc(&dh->deny); \
+ percpu_counter_inc(&dsh->deny); \
break; \
+ } \
} \
} while (0); \
RC; \
@@ -368,10 +376,15 @@ static int dynamic_vm_enough_memory_mm(struct mm_struct *mm, long pages)
return 1;
dh = &dynamic_hooks[DYNAMIC_SECURITY_HOOK_vm_enough_memory];
+ percpu_counter_inc(&dh->invocation);
list_for_each_entry(dsh, &dh->head, list) {
+ percpu_counter_inc(&dsh->invocation);
rc = dsh->hook.vm_enough_memory(mm, pages);
- if (rc <= 0)
+ if (rc <= 0) {
+ percpu_counter_inc(&dh->deny);
+ percpu_counter_inc(&dsh->deny);
break;
+ }
}
return rc;
}
@@ -1215,7 +1228,9 @@ static int dynamic_task_prctl(int option, unsigned long arg2,
goto out;
dh = &dynamic_hooks[DYNAMIC_SECURITY_HOOK_task_prctl];
+ percpu_counter_inc(&dh->invocation);
list_for_each_entry(dsh, &dh->head, list) {
+ percpu_counter_inc(&dsh->invocation);
thisrc = dsh->hook.task_prctl(option, arg2, arg3, arg4, arg5);
if (thisrc != -ENOSYS) {
rc = thisrc;
--
2.14.1
--
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