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Message-Id: <c089f67baff5abb060b0c1ba47273b2aa8cc6c41.1608225886.git.rgb@redhat.com>
Date: Mon, 21 Dec 2020 11:55:43 -0500
From: Richard Guy Briggs <rgb@...hat.com>
To: Linux Containers List <containers@...ts.linux-foundation.org>,
Linux API <linux-api@...r.kernel.org>,
Linux-Audit Mailing List <linux-audit@...hat.com>,
Linux FSdevel <linux-fsdevel@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Linux NetDev Upstream Mailing List <netdev@...r.kernel.org>,
Netfilter Devel List <netfilter-devel@...r.kernel.org>
Cc: Neil Horman <nhorman@...driver.com>,
David Howells <dhowells@...hat.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Simo Sorce <simo@...hat.com>,
Eric Paris <eparis@...isplace.org>, mpatel@...hat.com,
Serge Hallyn <serge@...lyn.com>,
Kees Cook <keescook@...omium.org>,
Jens Axboe <axboe@...nel.dk>,
Christian Brauner <christian.brauner@...ntu.com>,
Richard Guy Briggs <rgb@...hat.com>
Subject: [PATCH ghak90 v10 09/11] audit: contid check descendancy and nesting
Require the target task to be a descendant of the container
orchestrator/engine.
You would only change the audit container ID from one set or inherited
value to another if you were nesting containers.
If changing the contid, the container orchestrator/engine must be a
descendant and not same orchestrator as the one that set it so it is not
possible to change the contid of another orchestrator's container.
Since the task_is_descendant() function is used in YAMA and in audit,
remove the duplication and pull the function into kernel/core/sched.c
Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
---
include/linux/sched.h | 3 +++
kernel/audit.c | 26 +++++++++++++++++++++++---
kernel/sched/core.c | 33 +++++++++++++++++++++++++++++++++
security/yama/yama_lsm.c | 33 ---------------------------------
4 files changed, 59 insertions(+), 36 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b28348868b27..9e658e724543 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2055,4 +2055,7 @@ int sched_trace_rq_nr_running(struct rq *rq);
const struct cpumask *sched_trace_rd_span(struct root_domain *rd);
+extern int task_is_descendant(struct task_struct *parent,
+ struct task_struct *child);
+
#endif
diff --git a/kernel/audit.c b/kernel/audit.c
index 8d03f07e7128..6eed8ed0cc8e 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -475,11 +475,13 @@ void audit_free(struct task_struct *tsk)
rcu_read_lock();
cont = _audit_contobj_get_bytask(tsk);
rcu_read_unlock();
- spin_lock_irqsave(&_audit_contobj_list_lock, flags);
if (ns) {
audit_netns_contid_del(ns->net_ns, cont);
+ spin_lock_irqsave(&_audit_contobj_list_lock, flags);
_audit_contobj_put(cont);
+ spin_unlock_irqrestore(&_audit_contobj_list_lock, flags);
}
+ spin_lock_irqsave(&_audit_contobj_list_lock, flags);
_audit_contobj_put(cont);
spin_unlock_irqrestore(&_audit_contobj_list_lock, flags);
audit_free_syscall(tsk);
@@ -2923,6 +2925,21 @@ int audit_signal_info(int sig, struct task_struct *t)
return audit_signal_info_syscall(t);
}
+static bool audit_contid_isnesting(struct task_struct *tsk)
+{
+ bool isowner = false;
+ bool ownerisparent = false;
+ struct audit_task_info *info = tsk->audit;
+
+ rcu_read_lock();
+ if (info && info->cont) {
+ isowner = current == info->cont->owner;
+ ownerisparent = task_is_descendant(info->cont->owner, current);
+ }
+ rcu_read_unlock();
+ return !isowner && ownerisparent;
+}
+
/*
* audit_set_contid - set current task's audit contid
* @tsk: target task
@@ -2963,8 +2980,11 @@ int audit_set_contid(struct task_struct *tsk, u64 contid)
!(thread_group_leader(tsk) && thread_group_empty(tsk))) {
/* if task has children or is not single-threaded, deny */
rc = -EBUSY;
- } else if (info->cont) {
- /* if contid is already set, deny */
+ } else if (tsk == current || !task_is_descendant(current, tsk)) {
+ /* if task is not descendant, block */
+ rc = -EXDEV;
+ } else if (info->cont && !audit_contid_isnesting(tsk)) {
+ /* only allow contid setting again if nesting */
rc = -EEXIST;
}
rcu_read_lock();
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d2003a7d5ab5..6af7e6ee2498 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8436,6 +8436,39 @@ void dump_cpu_task(int cpu)
sched_show_task(cpu_curr(cpu));
}
+/*
+ * task_is_descendant - walk up a process family tree looking for a match
+ * @parent: the process to compare against while walking up from child
+ * @child: the process to start from while looking upwards for parent
+ *
+ * Returns 1 if child is a descendant of parent, 0 if not.
+ */
+int task_is_descendant(struct task_struct *parent,
+ struct task_struct *child)
+{
+ int rc = 0;
+ struct task_struct *walker = child;
+
+ if (!parent || !child)
+ return 0;
+
+ rcu_read_lock();
+ if (!thread_group_leader(parent))
+ parent = rcu_dereference(parent->group_leader);
+ while (walker->pid > 0) {
+ if (!thread_group_leader(walker))
+ walker = rcu_dereference(walker->group_leader);
+ if (walker == parent) {
+ rc = 1;
+ break;
+ }
+ walker = rcu_dereference(walker->real_parent);
+ }
+ rcu_read_unlock();
+
+ return rc;
+}
+
/*
* Nice levels are multiplicative, with a gentle 10% change for every
* nice level changed. I.e. when a CPU-bound task goes from nice 0 to
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 06e226166aab..2930e42eafc2 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -262,39 +262,6 @@ static int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
return rc;
}
-/**
- * task_is_descendant - walk up a process family tree looking for a match
- * @parent: the process to compare against while walking up from child
- * @child: the process to start from while looking upwards for parent
- *
- * Returns 1 if child is a descendant of parent, 0 if not.
- */
-static int task_is_descendant(struct task_struct *parent,
- struct task_struct *child)
-{
- int rc = 0;
- struct task_struct *walker = child;
-
- if (!parent || !child)
- return 0;
-
- rcu_read_lock();
- if (!thread_group_leader(parent))
- parent = rcu_dereference(parent->group_leader);
- while (walker->pid > 0) {
- if (!thread_group_leader(walker))
- walker = rcu_dereference(walker->group_leader);
- if (walker == parent) {
- rc = 1;
- break;
- }
- walker = rcu_dereference(walker->real_parent);
- }
- rcu_read_unlock();
-
- return rc;
-}
-
/**
* ptracer_exception_found - tracer registered as exception for this tracee
* @tracer: the task_struct of the process attempting ptrace
--
2.18.4
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