security: introducing security_request_module

Calling request_module() will trigger a userspace upcall which will load a
new module into the kernel.  This can be a dangerous event if the process
able to trigger request_module() is able to control either the modprobe
binary or the module binary.  This patch adds a new security hook to
request_module() which can be used by an LSM to control a processes ability
to call request_module().

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

diff --git a/include/linux/security.h b/include/linux/security.h
index 57ead99..1e3dd86 100644 (file)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -678,6 +678,9 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
  *     @inode points to the inode to use as a reference.
  *     The current task must be the one that nominated @inode.
  *     Return 0 if successful.
+ * @kernel_module_request:
+ *     Ability to trigger the kernel to automatically upcall to userspace for
+ *     userspace to load a kernel module with the given name.
  * @task_setuid:
  *     Check permission before setting one or more of the user identity
  *     attributes of the current process.  The @flags parameter indicates
@@ -1489,6 +1492,7 @@ struct security_operations {
        void (*cred_commit)(struct cred *new, const struct cred *old);
        int (*kernel_act_as)(struct cred *new, u32 secid);
        int (*kernel_create_files_as)(struct cred *new, struct inode *inode);
+       int (*kernel_module_request)(void);
        int (*task_setuid) (uid_t id0, uid_t id1, uid_t id2, int flags);
        int (*task_fix_setuid) (struct cred *new, const struct cred *old,
                                int flags);
@@ -1741,6 +1745,7 @@ int security_prepare_creds(struct cred *new, const struct cred *old, gfp_t gfp);
 void security_commit_creds(struct cred *new, const struct cred *old);
 int security_kernel_act_as(struct cred *new, u32 secid);
 int security_kernel_create_files_as(struct cred *new, struct inode *inode);
+int security_kernel_module_request(void);
 int security_task_setuid(uid_t id0, uid_t id1, uid_t id2, int flags);
 int security_task_fix_setuid(struct cred *new, const struct cred *old,
                             int flags);
@@ -2292,6 +2297,11 @@ static inline int security_kernel_create_files_as(struct cred *cred,
        return 0;
 }
 
+static inline int security_kernel_module_request(void)
+{
+       return 0;
+}
+
 static inline int security_task_setuid(uid_t id0, uid_t id1, uid_t id2,
                                       int flags)
 {

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 385c31a..5a7ae57 100644 (file)
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -78,6 +78,10 @@ int __request_module(bool wait, const char *fmt, ...)
 #define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
        static int kmod_loop_msg;
 
+       ret = security_kernel_module_request();
+       if (ret)
+               return ret;
+
        va_start(args, fmt);
        ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
        va_end(args);

diff --git a/security/capability.c b/security/capability.c
index ec05730..1b943f5 100644 (file)
--- a/security/capability.c
+++ b/security/capability.c
@@ -396,6 +396,11 @@ static int cap_kernel_create_files_as(struct cred *new, struct inode *inode)
        return 0;
 }
 
+static int cap_kernel_module_request(void)
+{
+       return 0;
+}
+
 static int cap_task_setuid(uid_t id0, uid_t id1, uid_t id2, int flags)
 {
        return 0;
@@ -945,6 +950,7 @@ void security_fixup_ops(struct security_operations *ops)
        set_to_cap_if_null(ops, cred_commit);
        set_to_cap_if_null(ops, kernel_act_as);
        set_to_cap_if_null(ops, kernel_create_files_as);
+       set_to_cap_if_null(ops, kernel_module_request);
        set_to_cap_if_null(ops, task_setuid);
        set_to_cap_if_null(ops, task_fix_setuid);
        set_to_cap_if_null(ops, task_setgid);

diff --git a/security/security.c b/security/security.c
index 4501c5e..0e993f4 100644 (file)
--- a/security/security.c
+++ b/security/security.c
@@ -709,6 +709,11 @@ int security_kernel_create_files_as(struct cred *new, struct inode *inode)
        return security_ops->kernel_create_files_as(new, inode);
 }
 
+int security_kernel_module_request(void)
+{
+       return security_ops->kernel_module_request();
+}
+
 int security_task_setuid(uid_t id0, uid_t id1, uid_t id2, int flags)
 {
        return security_ops->task_setuid(id0, id1, id2, flags);