security: create task_free security callback

The current LSM interface to cred_free is not sufficient for allowing
an LSM to track the life and death of a task. This patch adds the
task_free hook so that an LSM can clean up resources on task death.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/security.h b/include/linux/security.h
index 83c18e8c846d..8325eddd9ee4 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -651,6 +651,10 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
  *      manual page for definitions of the @clone_flags.
  *      @clone_flags contains the flags indicating what should be shared.
  *      Return 0 if permission is granted.
+ * @task_free:
+ *      @task task being freed
+ *      Handle release of task-related resources. (Note that this can be called
+ *      from interrupt context.)
  * @cred_alloc_blank:
  *      @cred points to the credentials.
  *      @gfp indicates the atomicity of any memory allocations.
@@ -1493,6 +1497,7 @@ struct security_operations {
         int (*dentry_open) (struct file *file, const struct cred *cred);
 
         int (*task_create) (unsigned long clone_flags);
+        void (*task_free) (struct task_struct *task);
         int (*cred_alloc_blank) (struct cred *cred, gfp_t gfp);
         void (*cred_free) (struct cred *cred);
         int (*cred_prepare)(struct cred *new, const struct cred *old,
@@ -1752,6 +1757,7 @@ int security_file_send_sigiotask(struct task_struct *tsk,
 int security_file_receive(struct file *file);
 int security_dentry_open(struct file *file, const struct cred *cred);
 int security_task_create(unsigned long clone_flags);
+void security_task_free(struct task_struct *task);
 int security_cred_alloc_blank(struct cred *cred, gfp_t gfp);
 void security_cred_free(struct cred *cred);
 int security_prepare_creds(struct cred *new, const struct cred *old, gfp_t gfp);
@@ -2245,6 +2251,9 @@ static inline int security_task_create(unsigned long clone_flags)
         return 0;
 }
 
+static inline void security_task_free(struct task_struct *task)
+{ }
+
 static inline int security_cred_alloc_blank(struct cred *cred, gfp_t gfp)
 {
         return 0;