[PATCH v4a 8/8] module: replace the existing LSM hook in init_module

Mimi Zohar
2018-05-31T15:24:09Z

Both the init_module and finit_module syscalls call either directly
or indirectly the security_kernel_read_file LSM hook. This patch
replaces the direct call in init_module with a call to the new
security_kernel_load_data hook and makes the corresponding changes
in SELinux, LoadPin, and IMA.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Jeff Vander Stoep <jeffv@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: Kees Cook <keescook@chromium.org>

---
Changelog:
- For SELinux, have both the security_kernel_read_file and
security_kernel_load_data LSM hooks call selinux_kernel_read_file().
- LoadPin: replace existing init_module LSM hook support with
new security_kernel_load_data hook.

kernel/module.c | 2 +-
security/integrity/ima/ima_main.c | 24 ++++++++++--------------
security/loadpin/loadpin.c | 15 +++++++++++++++
security/selinux/hooks.c | 15 +++++++++++++++
4 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index ce8066b88178..b97c642b5b4d 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2879,7 +2879,7 @@ static int copy_module_from_user(const void __user *umod, unsigned long len,
if (info->len < sizeof(*(info->hdr)))
return -ENOEXEC;

- err = security_kernel_read_file(NULL, READING_MODULE);
+ err = security_kernel_load_data(LOADING_MODULE);
if (err)
return err;

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 5a7696152982..cd33a2eff496 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -438,17 +438,6 @@ static int read_idmap[READING_MAX_ID] = {
*/
int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
{
- bool sig_enforce = is_module_sig_enforced();
-
- if (!file && read_id == READING_MODULE) {
- if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES) &&
- (ima_appraise & IMA_APPRAISE_ENFORCE)) {
- pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
- return -EACCES; /* INTEGRITY_UNKNOWN */
- }
- return 0; /* We rely on module signature checking */
- }
-
if (read_id == READING_FIRMWARE_PREALLOC_BUFFER) {
if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
(ima_appraise & IMA_APPRAISE_ENFORCE)) {
@@ -487,9 +476,6 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
return 0;
}

- if (!file && read_id == READING_MODULE) /* MODULE_SIG_FORCE enabled */
- return 0;
-
/* permit signed certs */
if (!file && read_id == READING_X509_CERTIFICATE)
return 0;
@@ -518,6 +504,8 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
*/
int ima_load_data(enum kernel_load_data_id id)
{
+ bool sig_enforce;
+
if ((ima_appraise & IMA_APPRAISE_ENFORCE) != IMA_APPRAISE_ENFORCE)
return 0;

@@ -533,6 +521,14 @@ int ima_load_data(enum kernel_load_data_id id)
pr_err("Prevent firmware sysfs fallback loading.\n");
return -EACCES; /* INTEGRITY_UNKNOWN */
}
+ break;
+ case LOADING_MODULE:
+ sig_enforce = is_module_sig_enforced();
+
+ if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES)) {
+ pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
+ return -EACCES; /* INTEGRITY_UNKNOWN */
+ }
default:
break;
}
diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
index 5fa191252c8f..a9c07bfbc338 100644
--- a/security/loadpin/loadpin.c
+++ b/security/loadpin/loadpin.c
@@ -173,9 +173,24 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
return 0;
}

+static int loadpin_load_data(enum kernel_load_data_id id)
+{
+ int rc = 0;
+
+ switch (id) {
+ case LOADING_MODULE:
+ rc = loadpin_read_file(NULL, READING_MODULE);
+ default:
+ break;
+ }
+
+ return rc;
+}
+
static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(sb_free_security, loadpin_sb_free_security),
LSM_HOOK_INIT(kernel_read_file, loadpin_read_file),
+ LSM_HOOK_INIT(kernel_load_data, loadpin_load_data),
};

void __init loadpin_add_hooks(void)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 02ebd1585eaf..475aed9ee2c7 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -4059,6 +4059,20 @@ static int selinux_kernel_read_file(struct file *file,
return rc;
}

+static int selinux_kernel_load_data(enum kernel_load_data_id id)
+{
+ int rc = 0;
+
+ switch (id) {
+ case LOADING_MODULE:
+ rc = selinux_kernel_module_from_file(NULL);
+ default:
+ break;
+ }
+
+ return rc;
+}
+
static int selinux_task_setpgid(struct task_struct *p, pid_t pgid)
{
return avc_has_perm(&selinux_state,
@@ -6950,6 +6964,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(kernel_act_as, selinux_kernel_act_as),
LSM_HOOK_INIT(kernel_create_files_as, selinux_kernel_create_files_as),
LSM_HOOK_INIT(kernel_module_request, selinux_kernel_module_request),
+ LSM_HOOK_INIT(kernel_load_data, selinux_kernel_load_data),
LSM_HOOK_INIT(kernel_read_file, selinux_kernel_read_file),
LSM_HOOK_INIT(task_setpgid, selinux_task_setpgid),
LSM_HOOK_INIT(task_getpgid, selinux_task_getpgid),
--
2.7.5