Return EPERM not ECHILD on security_task_wait failure (73243284) · Commits · 戴 / test

wait* syscalls return -ECHILD even when an individual PID of a live child was requested explicitly, when security_task_wait denies the operation. This means that something like a broken SELinux policy can produce an unexpected failure that looks just like a bug with wait or ptrace or something. This patch makes do_wait return -EACCES (or other appropriate error returned from security_task_wait() instead of -ECHILD if some children were ruled out solely because security_task_wait failed. [jmorris@namei.org: switch error code to EACCES] Signed-off-by:

Roland McGrath <roland@redhat.com> Acked-by:

Stephen Smalley <sds@tycho.nsa.gov> Cc: Chris Wright <chrisw@sous-sol.org> Cc: James Morris <jmorris@namei.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

kernel/exit.c

+15 −2

Original line number	Diff line number	Diff line
		@@ -1033,6 +1033,8 @@ asmlinkage void sys_exit_group(int error_code)

		static int eligible_child(pid_t pid, int options, struct task_struct *p)
		{
		int err;

		if (pid > 0) {
		if (p->pid != pid)
		return 0;
		@@ -1066,8 +1068,9 @@ static int eligible_child(pid_t pid, int options, struct task_struct *p)
		if (delay_group_leader(p))
		return 2;

		if (security_task_wait(p))
		return 0;
		err = security_task_wait(p);
		if (err)
		return err;

		return 1;
		}
		@@ -1449,6 +1452,7 @@ static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
		DECLARE_WAITQUEUE(wait, current);
		struct task_struct *tsk;
		int flag, retval;
		int allowed, denied;

		add_wait_queue(&current->signal->wait_chldexit,&wait);
		repeat:
		@@ -1457,6 +1461,7 @@ repeat:
		* match our criteria, even if we are not able to reap it yet.
		*/
		flag = 0;
		allowed = denied = 0;
		current->state = TASK_INTERRUPTIBLE;
		read_lock(&tasklist_lock);
		tsk = current;
		@@ -1472,6 +1477,12 @@ repeat:
		if (!ret)
		continue;

		if (unlikely(ret < 0)) {
		denied = ret;
		continue;
		}
		allowed = 1;

		switch (p->state) {
		case TASK_TRACED:
		/*
		@@ -1570,6 +1581,8 @@ check_continued:
		goto repeat;
		}
		retval = -ECHILD;
		if (unlikely(denied) && !allowed)
		retval = denied;
		end:
		current->state = TASK_RUNNING;
		remove_wait_queue(&current->signal->wait_chldexit,&wait);

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