[PATCH ghak90 (was ghak32) V4 01/10] audit: collect audit task parameters

Richard Guy Briggs
2018-07-31T20:07:36Z

The audit-related parameters in struct task_struct should ideally be
collected together and accessed through a standard audit API.

Collect the existing loginuid, sessionid and audit_context together in a
new struct audit_task_info called "audit" in struct task_struct.

Use kmem_cache to manage this pool of memory.
Un-inline audit_free() to be able to always recover that memory.

See: https://github.com/linux-audit/audit-kernel/issues/81

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
---
include/linux/audit.h | 34 ++++++++++++++++++++++++----------
include/linux/sched.h | 5 +----
init/init_task.c | 3 +--
init/main.c | 2 ++
kernel/auditsc.c | 51 ++++++++++++++++++++++++++++++++++++++++++---------
kernel/fork.c | 4 +++-
6 files changed, 73 insertions(+), 26 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 9334fbe..8964332 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -219,8 +219,15 @@ static inline void audit_log_task_info(struct audit_buffer *ab,

/* These are defined in auditsc.c */
/* Public API */
+struct audit_task_info {
+ kuid_t loginuid;
+ unsigned int sessionid;
+ struct audit_context *ctx;
+};
+extern struct audit_task_info init_struct_audit;
+extern void __init audit_task_init(void);
extern int audit_alloc(struct task_struct *task);
-extern void __audit_free(struct task_struct *task);
+extern void audit_free(struct task_struct *task);
extern void __audit_syscall_entry(int major, unsigned long a0, unsigned long a1,
unsigned long a2, unsigned long a3);
extern void __audit_syscall_exit(int ret_success, long ret_value);
@@ -242,12 +249,15 @@ extern void audit_seccomp_actions_logged(const char *names,

static inline void audit_set_context(struct task_struct *task, struct audit_context *ctx)
{
- task->audit_context = ctx;
+ task->audit->ctx = ctx;
}

static inline struct audit_context *audit_context(void)
{
- return current->audit_context;
+ if (current->audit)
+ return current->audit->ctx;
+ else
+ return NULL;
}

static inline bool audit_dummy_context(void)
@@ -255,11 +265,7 @@ static inline bool audit_dummy_context(void)
void *p = audit_context();
return !p || *(int *)p;
}
-static inline void audit_free(struct task_struct *task)
-{
- if (unlikely(task->audit_context))
- __audit_free(task);
-}
+
static inline void audit_syscall_entry(int major, unsigned long a0,
unsigned long a1, unsigned long a2,
unsigned long a3)
@@ -331,12 +337,18 @@ extern int auditsc_get_stamp(struct audit_context *ctx,

static inline kuid_t audit_get_loginuid(struct task_struct *tsk)
{
- return tsk->loginuid;
+ if (tsk->audit)
+ return tsk->audit->loginuid;
+ else
+ return INVALID_UID;
}

static inline unsigned int audit_get_sessionid(struct task_struct *tsk)
{
- return tsk->sessionid;
+ if (tsk->audit)
+ return tsk->audit->sessionid;
+ else
+ return AUDIT_SID_UNSET;
}

extern void __audit_ipc_obj(struct kern_ipc_perm *ipcp);
@@ -461,6 +473,8 @@ static inline void audit_fanotify(unsigned int response)
extern int audit_n_rules;
extern int audit_signals;
#else /* CONFIG_AUDITSYSCALL */
+static inline void __init audit_task_init(void)
+{ }
static inline int audit_alloc(struct task_struct *task)
{
return 0;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 87bf02d..e117272 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -30,7 +30,6 @@
#include <linux/rseq.h>

/* task_struct member predeclarations (sorted alphabetically): */
-struct audit_context;
struct backing_dev_info;
struct bio_list;
struct blk_plug;
@@ -873,10 +872,8 @@ struct task_struct {

struct callback_head *task_works;

- struct audit_context *audit_context;
#ifdef CONFIG_AUDITSYSCALL
- kuid_t loginuid;
- unsigned int sessionid;
+ struct audit_task_info *audit;
#endif
struct seccomp seccomp;

diff --git a/init/init_task.c b/init/init_task.c
index 74f60ba..4058840 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -119,8 +119,7 @@ struct task_struct init_task
.thread_group = LIST_HEAD_INIT(init_task.thread_group),
.thread_node = LIST_HEAD_INIT(init_signals.thread_head),
#ifdef CONFIG_AUDITSYSCALL
- .loginuid = INVALID_UID,
- .sessionid = AUDIT_SID_UNSET,
+ .audit = &init_struct_audit,
#endif
#ifdef CONFIG_PERF_EVENTS
.perf_event_mutex = __MUTEX_INITIALIZER(init_task.perf_event_mutex),
diff --git a/init/main.c b/init/main.c
index 3b4ada1..6aba171 100644
--- a/init/main.c
+++ b/init/main.c
@@ -92,6 +92,7 @@
#include <linux/rodata_test.h>
#include <linux/jump_label.h>
#include <linux/mem_encrypt.h>
+#include <linux/audit.h>

#include <asm/io.h>
#include <asm/bugs.h>
@@ -721,6 +722,7 @@ asmlinkage __visible void __init start_kernel(void)
nsfs_init();
cpuset_init();
cgroup_init();
+ audit_task_init();
taskstats_init_early();
delayacct_init();

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index fb20746..88779a7 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -841,7 +841,7 @@ static inline struct audit_context *audit_take_context(struct task_struct *tsk,
int return_valid,
long return_code)
{
- struct audit_context *context = tsk->audit_context;
+ struct audit_context *context = tsk->audit->ctx;

if (!context)
return NULL;
@@ -926,6 +926,15 @@ static inline struct audit_context *audit_alloc_context(enum audit_state state)
return context;
}

+static struct kmem_cache *audit_task_cache;
+
+void __init audit_task_init(void)
+{
+ audit_task_cache = kmem_cache_create("audit_task",
+ sizeof(struct audit_task_info),
+ 0, SLAB_PANIC, NULL);
+}
+
/**
* audit_alloc - allocate an audit context block for a task
* @tsk: task
@@ -940,17 +949,28 @@ int audit_alloc(struct task_struct *tsk)
struct audit_context *context;
enum audit_state state;
char *key = NULL;
+ struct audit_task_info *info;
+
+ info = kmem_cache_zalloc(audit_task_cache, GFP_KERNEL);
+ if (!info)
+ return -ENOMEM;
+ info->loginuid = audit_get_loginuid(current);
+ info->sessionid = audit_get_sessionid(current);
+ tsk->audit = info;

if (likely(!audit_ever_enabled))
return 0; /* Return if not auditing. */

state = audit_filter_task(tsk, &key);
if (state == AUDIT_DISABLED) {
+ audit_set_context(tsk, NULL);
clear_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT);
return 0;
}

if (!(context = audit_alloc_context(state))) {
+ tsk->audit = NULL;
+ kmem_cache_free(audit_task_cache, info);
kfree(key);
audit_log_lost("out of memory in audit_alloc");
return -ENOMEM;
@@ -962,6 +982,12 @@ int audit_alloc(struct task_struct *tsk)
return 0;
}

+struct audit_task_info init_struct_audit = {
+ .loginuid = INVALID_UID,
+ .sessionid = AUDIT_SID_UNSET,
+ .ctx = NULL,
+};
+
static inline void audit_free_context(struct audit_context *context)
{
audit_free_names(context);
@@ -1469,26 +1495,33 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
}

/**
- * __audit_free - free a per-task audit context
+ * audit_free - free a per-task audit context
* @tsk: task whose audit context block to free
*
* Called from copy_process and do_exit
*/
-void __audit_free(struct task_struct *tsk)
+void audit_free(struct task_struct *tsk)
{
struct audit_context *context;
+ struct audit_task_info *info;

context = audit_take_context(tsk, 0, 0);
- if (!context)
- return;
-
/* Check for system calls that do not go through the exit
* function (e.g., exit_group), then free context block.
* We use GFP_ATOMIC here because we might be doing this
* in the context of the idle thread */
/* that can happen only if we are called from do_exit() */
- if (context->in_syscall && context->current_state == AUDIT_RECORD_CONTEXT)
+ if (context && context->in_syscall &&
+ context->current_state == AUDIT_RECORD_CONTEXT)
audit_log_exit(context, tsk);
+ /* Freeing the audit_task_info struct must be performed after
+ * audit_log_exit() due to need for loginuid and sessionid.
+ */
+ info = tsk->audit;
+ tsk->audit = NULL;
+ kmem_cache_free(audit_task_cache, info);
+ if (!context)
+ return;
if (!list_empty(&context->killed_trees))
audit_kill_trees(&context->killed_trees);

@@ -2071,8 +2104,8 @@ int audit_set_loginuid(kuid_t loginuid)
sessionid = (unsigned int)atomic_inc_return(&session_id);
}

- task->sessionid = sessionid;
- task->loginuid = loginuid;
+ task->audit->sessionid = sessionid;
+ task->audit->loginuid = loginuid;
out:
audit_log_set_loginuid(oldloginuid, loginuid, oldsessionid, sessionid, rc);
return rc;
diff --git a/kernel/fork.c b/kernel/fork.c
index 9440d61..1bfb0ff 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1721,7 +1721,9 @@ static __latent_entropy struct task_struct *copy_process(
p->start_time = ktime_get_ns();
p->real_start_time = ktime_get_boot_ns();
p->io_context = NULL;
- audit_set_context(p, NULL);
+#ifdef CONFIG_AUDITSYSCALL
+ p->audit = NULL;
+#endif /* CONFIG_AUDITSYSCALL */
cgroup_fork(p);
#ifdef CONFIG_NUMA
p->mempolicy = mpol_dup(p->mempolicy);
--
1.8.3.1