security,selinux,smack: kill security_task_wait hook
As reported by yangshukui, a permission denial from security_task_wait()
can lead to a soft lockup in zap_pid_ns_processes() since it only expects
sys_wait4() to return 0 or -ECHILD. Further, security_task_wait() can
in general lead to zombies; in the absence of some way to automatically
reparent a child process upon a denial, the hook is not useful. Remove
the security hook and its implementations in SELinux and Smack. Smack
already removed its check from its hook.
Reported-by: yangshukui <yangshukui@huawei.com>
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
diff --git a/kernel/exit.c b/kernel/exit.c
index 8f14b86..60f2451 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -14,7 +14,6 @@
#include <linux/tty.h>
#include <linux/iocontext.h>
#include <linux/key.h>
-#include <linux/security.h>
#include <linux/cpu.h>
#include <linux/acct.h>
#include <linux/tsacct_kern.h>
@@ -1360,7 +1359,7 @@ static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
* Returns nonzero for a final return, when we have unlocked tasklist_lock.
* Returns zero if the search for a child should continue;
* then ->notask_error is 0 if @p is an eligible child,
- * or another error from security_task_wait(), or still -ECHILD.
+ * or still -ECHILD.
*/
static int wait_consider_task(struct wait_opts *wo, int ptrace,
struct task_struct *p)
@@ -1380,20 +1379,6 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
if (!ret)
return ret;
- ret = security_task_wait(p);
- if (unlikely(ret < 0)) {
- /*
- * If we have not yet seen any eligible child,
- * then let this error code replace -ECHILD.
- * A permission error will give the user a clue
- * to look for security policy problems, rather
- * than for mysterious wait bugs.
- */
- if (wo->notask_error)
- wo->notask_error = ret;
- return 0;
- }
-
if (unlikely(exit_state == EXIT_TRACE)) {
/*
* ptrace == 0 means we are the natural parent. In this case
@@ -1486,7 +1471,7 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
* Returns nonzero for a final return, when we have unlocked tasklist_lock.
* Returns zero if the search for a child should continue; then
* ->notask_error is 0 if there were any eligible children,
- * or another error from security_task_wait(), or still -ECHILD.
+ * or still -ECHILD.
*/
static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
{