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Message-Id: <01229b93733d9baf6ac9bb0cc243eeb08ad579cd.1593198710.git.rgb@redhat.com>
Date: Sat, 27 Jun 2020 09:20:44 -0400
From: Richard Guy Briggs <rgb@...hat.com>
To: containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
Linux-Audit Mailing List <linux-audit@...hat.com>,
linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Cc: Paul Moore <paul@...l-moore.com>, sgrubb@...hat.com,
omosnace@...hat.com, dhowells@...hat.com, simo@...hat.com,
eparis@...isplace.org, serge@...lyn.com, ebiederm@...ssion.com,
nhorman@...driver.com, dwalsh@...hat.com, mpatel@...hat.com,
Richard Guy Briggs <rgb@...hat.com>
Subject: [PATCH ghak90 V9 11/13] 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 | 23 +++++++++++++++++++++--
kernel/sched/core.c | 33 +++++++++++++++++++++++++++++++++
security/yama/yama_lsm.c | 33 ---------------------------------
4 files changed, 57 insertions(+), 35 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2213ac670386..06938d0b9e0c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2047,4 +2047,7 @@ static inline void rseq_syscall(struct pt_regs *regs)
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 a862721dfd9b..efa65ec01239 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -2713,6 +2713,20 @@ 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;
+
+ rcu_read_lock();
+ if (tsk->audit && tsk->audit->cont) {
+ isowner = current == tsk->audit->cont->owner;
+ ownerisparent = task_is_descendant(tsk->audit->cont->owner, current);
+ }
+ rcu_read_unlock();
+ return !isowner && ownerisparent;
+}
+
/*
* audit_set_contid - set current task's audit contid
* @task: target task
@@ -2755,8 +2769,13 @@ int audit_set_contid(struct task_struct *task, u64 contid)
rc = -EBUSY;
goto unlock;
}
- /* if contid is already set, deny */
- if (audit_contid_set(task))
+ /* if task is not descendant, block */
+ if (task == current || !task_is_descendant(current, task)) {
+ rc = -EXDEV;
+ goto unlock;
+ }
+ /* only allow contid setting again if nesting */
+ if (audit_contid_set(task) && !audit_contid_isnesting(task))
rc = -EEXIST;
unlock:
read_unlock(&tasklist_lock);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 8f360326861e..e6b24c52b3c3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8012,6 +8012,39 @@ void dump_cpu_task(int 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
* nice 1, it will get ~10% less CPU time than another CPU-bound task
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 536c99646f6a..24939f765df5 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -263,39 +263,6 @@ static int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
}
/**
- * 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
* @tracee: the task_struct of the process to be ptraced
--
1.8.3.1
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