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/${HOOK_NAME} which has the currently attached LSMs for that given hook.
Not only does it list which LSMs are hooked into each dynamic hook, but it also lists the global accept / deny count, as well as the per-hook accept / deny count. The earlier is useful to keep consistent statistics across the attachment, and unattachment of LSMs. Signed-off-by: Sargun Dhillon <sar...@sargun.me> --- security/Kconfig | 7 +++ security/Makefile | 1 + security/dynamic.h | 9 ++++ security/dynamicfs.c | 118 +++++++++++++++++++++++++++++++++++++++++++++++++++ security/inode.c | 2 + 5 files changed, 137 insertions(+) create mode 100644 security/dynamicfs.c diff --git a/security/Kconfig b/security/Kconfig index 77841bd..d6c579d 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -94,6 +94,13 @@ config SECURITY_DYNAMIC_HOOKS They cannot circumvent the built-in LSMs. If you are unsure how to answer this question, answer N. +config SECURITY_DYNAMIC_HOOKS_FS + bool + default y if SECURITY_DYNAMIC_HOOKS && SECURITYFS + depends on SECURITY_DYNAMIC_HOOKS && SECURITYFS + help + This option enables listing of dynamically loaded LSM hooks. + config INTEL_TXT bool "Enable Intel(R) Trusted Execution Technology (Intel(R) TXT)" depends on HAVE_INTEL_TXT diff --git a/security/Makefile b/security/Makefile index 59e695a..51cbec0 100644 --- a/security/Makefile +++ b/security/Makefile @@ -19,6 +19,7 @@ obj-$(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.h b/security/dynamic.h index 6823e38..1362b08 100644 --- a/security/dynamic.h +++ b/security/dynamic.h @@ -13,6 +13,9 @@ 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; struct srcu_struct srcu; }; @@ -22,3 +25,9 @@ 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 0000000..a9292e2 --- /dev/null +++ b/security/dynamicfs.c @@ -0,0 +1,118 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/module.h> +#include <linux/fs.h> +#include <linux/srcu.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; + int srcu_lock_index; +}; + +static void *dynamic_hooks_sop_start(struct seq_file *s, loff_t *pos) +{ + struct seq_private_data *pd = s->private; + + pd->srcu_lock_index = srcu_read_lock(&pd->dh->srcu); + 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) +{ + struct seq_private_data *pd = s->private; + + srcu_read_unlock(&pd->dh->srcu, pd->srcu_lock_index); +} + +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 8dd9ca8..0862be1 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); -- 2.9.3