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Subject[PATCH ghak90 V8 04/16] audit: convert to contid list to check for orch/engine ownership
Date
Store the audit container identifier in a refcounted kernel object that
is added to the master list of audit container identifiers. This will
allow multiple container orchestrators/engines to work on the same
machine without danger of inadvertantly re-using an existing identifier.
It will also allow an orchestrator to inject a process into an existing
container by checking if the original container owner is the one
injecting the task. A hash table list is used to optimize searches.

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
---
include/linux/audit.h | 14 ++++++--
kernel/audit.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++---
kernel/audit.h | 8 +++++
3 files changed, 112 insertions(+), 8 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index a045b34ecf44..0e6dbe943ae4 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -94,10 +94,18 @@ struct audit_ntp_data {
struct audit_ntp_data {};
#endif

+struct audit_contobj {
+ struct list_head list;
+ u64 id;
+ struct task_struct *owner;
+ refcount_t refcount;
+ struct rcu_head rcu;
+};
+
struct audit_task_info {
kuid_t loginuid;
unsigned int sessionid;
- u64 contid;
+ struct audit_contobj *cont;
#ifdef CONFIG_AUDITSYSCALL
struct audit_context *ctx;
#endif
@@ -203,9 +211,9 @@ static inline unsigned int audit_get_sessionid(struct task_struct *tsk)

static inline u64 audit_get_contid(struct task_struct *tsk)
{
- if (!tsk->audit)
+ if (!tsk->audit || !tsk->audit->cont)
return AUDIT_CID_UNSET;
- return tsk->audit->contid;
+ return tsk->audit->cont->id;
}

extern u32 audit_enabled;
diff --git a/kernel/audit.c b/kernel/audit.c
index 2d7707426b7d..4bab20f5f781 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -138,6 +138,12 @@ struct auditd_connection {

/* Hash for inode-based rules */
struct list_head audit_inode_hash[AUDIT_INODE_BUCKETS];
+/* Hash for contid object lists */
+struct list_head audit_contid_hash[AUDIT_CONTID_BUCKETS];
+/* Lock all additions and deletions to the contid hash lists, assignment
+ * of container objects to tasks and refcount changes. There should be
+ * no need for interaction with tasklist_lock */
+static DEFINE_SPINLOCK(audit_contobj_list_lock);

static struct kmem_cache *audit_buffer_cache;

@@ -212,6 +218,31 @@ void __init audit_task_init(void)
0, SLAB_PANIC, NULL);
}

+static struct audit_contobj *_audit_contobj(struct task_struct *tsk)
+{
+ if (!tsk->audit)
+ return NULL;
+ return tsk->audit->cont;
+}
+
+/* audit_contobj_list_lock must be held by caller unless new */
+static void _audit_contobj_hold(struct audit_contobj *cont)
+{
+ refcount_inc(&cont->refcount);
+}
+
+/* audit_contobj_list_lock must be held by caller */
+static void _audit_contobj_put(struct audit_contobj *cont)
+{
+ if (!cont)
+ return;
+ if (refcount_dec_and_test(&cont->refcount)) {
+ put_task_struct(cont->owner);
+ list_del_rcu(&cont->list);
+ kfree_rcu(cont, rcu);
+ }
+}
+
/**
* audit_alloc - allocate an audit info block for a task
* @tsk: task
@@ -232,7 +263,11 @@ int audit_alloc(struct task_struct *tsk)
}
info->loginuid = audit_get_loginuid(current);
info->sessionid = audit_get_sessionid(current);
- info->contid = audit_get_contid(current);
+ spin_lock(&audit_contobj_list_lock);
+ info->cont = _audit_contobj(current);
+ if (info->cont)
+ _audit_contobj_hold(info->cont);
+ spin_unlock(&audit_contobj_list_lock);
tsk->audit = info;

ret = audit_alloc_syscall(tsk);
@@ -247,7 +282,7 @@ int audit_alloc(struct task_struct *tsk)
struct audit_task_info init_struct_audit = {
.loginuid = INVALID_UID,
.sessionid = AUDIT_SID_UNSET,
- .contid = AUDIT_CID_UNSET,
+ .cont = NULL,
#ifdef CONFIG_AUDITSYSCALL
.ctx = NULL,
#endif
@@ -267,6 +302,9 @@ void audit_free(struct task_struct *tsk)
/* Freeing the audit_task_info struct must be performed after
* audit_log_exit() due to need for loginuid and sessionid.
*/
+ spin_lock(&audit_contobj_list_lock);
+ _audit_contobj_put(tsk->audit->cont);
+ spin_unlock(&audit_contobj_list_lock);
info = tsk->audit;
tsk->audit = NULL;
kmem_cache_free(audit_task_cache, info);
@@ -1658,6 +1696,9 @@ static int __init audit_init(void)
for (i = 0; i < AUDIT_INODE_BUCKETS; i++)
INIT_LIST_HEAD(&audit_inode_hash[i]);

+ for (i = 0; i < AUDIT_CONTID_BUCKETS; i++)
+ INIT_LIST_HEAD(&audit_contid_hash[i]);
+
mutex_init(&audit_cmd_mutex.lock);
audit_cmd_mutex.owner = NULL;

@@ -2365,6 +2406,9 @@ int audit_signal_info(int sig, struct task_struct *t)
*
* Returns 0 on success, -EPERM on permission failure.
*
+ * If the original container owner goes away, no task injection is
+ * possible to an existing container.
+ *
* Called (set) from fs/proc/base.c::proc_contid_write().
*/
int audit_set_contid(struct task_struct *task, u64 contid)
@@ -2381,9 +2425,12 @@ int audit_set_contid(struct task_struct *task, u64 contid)
}
oldcontid = audit_get_contid(task);
read_lock(&tasklist_lock);
- /* Don't allow the audit containerid to be unset */
+ /* Don't allow the contid to be unset */
if (!audit_contid_valid(contid))
rc = -EINVAL;
+ /* Don't allow the contid to be set to the same value again */
+ else if (contid == oldcontid) {
+ rc = -EADDRINUSE;
/* if we don't have caps, reject */
else if (!capable(CAP_AUDIT_CONTROL))
rc = -EPERM;
@@ -2396,8 +2443,49 @@ int audit_set_contid(struct task_struct *task, u64 contid)
else if (audit_contid_set(task))
rc = -ECHILD;
read_unlock(&tasklist_lock);
- if (!rc)
- task->audit->contid = contid;
+ if (!rc) {
+ struct audit_contobj *oldcont = _audit_contobj(task);
+ struct audit_contobj *cont = NULL, *newcont = NULL;
+ int h = audit_hash_contid(contid);
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(cont, &audit_contid_hash[h], list)
+ if (cont->id == contid) {
+ /* task injection to existing container */
+ if (current == cont->owner) {
+ spin_lock(&audit_contobj_list_lock);
+ _audit_contobj_hold(cont);
+ spin_unlock(&audit_contobj_list_lock);
+ newcont = cont;
+ } else {
+ rc = -ENOTUNIQ;
+ goto conterror;
+ }
+ break;
+ }
+ if (!newcont) {
+ newcont = kmalloc(sizeof(*newcont), GFP_ATOMIC);
+ if (newcont) {
+ INIT_LIST_HEAD(&newcont->list);
+ newcont->id = contid;
+ get_task_struct(current);
+ newcont->owner = current;
+ refcount_set(&newcont->refcount, 1);
+ spin_lock(&audit_contobj_list_lock);
+ list_add_rcu(&newcont->list, &audit_contid_hash[h]);
+ spin_unlock(&audit_contobj_list_lock);
+ } else {
+ rc = -ENOMEM;
+ goto conterror;
+ }
+ }
+ task->audit->cont = newcont;
+ spin_lock(&audit_contobj_list_lock);
+ _audit_contobj_put(oldcont);
+ spin_unlock(&audit_contobj_list_lock);
+conterror:
+ rcu_read_unlock();
+ }
task_unlock(task);

if (!audit_enabled)
diff --git a/kernel/audit.h b/kernel/audit.h
index 16bd03b88e0d..e4a31aa92dfe 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -211,6 +211,14 @@ static inline int audit_hash_ino(u32 ino)
return (ino & (AUDIT_INODE_BUCKETS-1));
}

+#define AUDIT_CONTID_BUCKETS 32
+extern struct list_head audit_contid_hash[AUDIT_CONTID_BUCKETS];
+
+static inline int audit_hash_contid(u64 contid)
+{
+ return (contid & (AUDIT_CONTID_BUCKETS-1));
+}
+
/* Indicates that audit should log the full pathname. */
#define AUDIT_NAME_FULL -1

--
1.8.3.1
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