[PATCH v4 8/8] module: replace the existing LSM hook in init_module

Mimi Zohar
2018-05-29T18:02:58Z

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 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>
---
kernel/module.c | 2 +-
security/integrity/ima/ima_main.c | 24 ++++++++++--------------
security/selinux/hooks.c | 26 ++++++++++++++++++++------
3 files changed, 31 insertions(+), 21 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 3dae605a1604..0ff1d8152f6e 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -441,17 +441,6 @@ 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)) {
@@ -490,9 +479,6 @@ 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;
@@ -521,6 +507,8 @@ 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;

@@ -536,6 +524,14 @@ 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/selinux/hooks.c b/security/selinux/hooks.c
index 02ebd1585eaf..e02186470fc5 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -4018,12 +4018,6 @@ static int selinux_kernel_module_from_file(struct file *file)
u32 sid = current_sid();
int rc;

- /* init_module */
- if (file == NULL)
- return avc_has_perm(&selinux_state,
- sid, sid, SECCLASS_SYSTEM,
- SYSTEM__MODULE_LOAD, NULL);
-
/* finit_module */

ad.type = LSM_AUDIT_DATA_FILE;
@@ -4043,6 +4037,25 @@ static int selinux_kernel_module_from_file(struct file *file)
SYSTEM__MODULE_LOAD, &ad);
}

+static int selinux_kernel_load_data(enum kernel_load_data_id id)
+{
+ u32 sid;
+ int rc = 0;
+
+ switch (id) {
+ case LOADING_MODULE:
+ sid = current_sid();
+
+ /* init_module */
+ return avc_has_perm(&selinux_state, sid, sid, SECCLASS_SYSTEM,
+ SYSTEM__MODULE_LOAD, NULL);
+ default:
+ break;
+ }
+
+ return rc;
+}
+
static int selinux_kernel_read_file(struct file *file,
enum kernel_read_file_id id)
{
@@ -6950,6 +6963,7 @@ 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