[PATCH] exec: allow init to exec from any thread. (fef23e7f) · Commits · 戴 / test

After looking at the problem of init calling exec some more I figured out an easy way to make the code work. The actual symptom without out this patch is that all threads will die except pid == 1, and the thread calling exec. The thread calling exec will wait forever for pid == 1 to die. Since pid == 1 does not install a handler for SIGKILL it will never die. This modifies the tests for init from current->pid == 1 to the equivalent current == child_reaper. And then it causes exec in the ugly case to modify child_reaper. The only weird symptom is that you wind up with an init process that doesn't have the oldest start time on the box. Signed-off-by:

Eric W. Biederman <ebiederm@xmission.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by:

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

Linus Torvalds <torvalds@osdl.org>

fs/exec.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -660,12 +660,23 @@ static int de_thread(struct task_struct *tsk)
		struct dentry proc_dentry1, proc_dentry2;
		unsigned long ptrace;

		leader = current->group_leader;
		/*
		* If our leader is the child_reaper become
		* the child_reaper and resend SIGKILL signal.
		*/
		if (unlikely(leader == child_reaper)) {
		write_lock(&tasklist_lock);
		child_reaper = current;
		zap_other_threads(current);
		write_unlock(&tasklist_lock);
		}

		/*
		* Wait for the thread group leader to be a zombie.
		* It should already be zombie at this point, most
		* of the time.
		*/
		leader = current->group_leader;
		while (leader->exit_state != EXIT_ZOMBIE)
		yield();

kernel/exit.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -807,7 +807,7 @@ fastcall NORET_TYPE void do_exit(long code)
		panic("Aiee, killing interrupt handler!");
		if (unlikely(!tsk->pid))
		panic("Attempted to kill the idle task!");
		if (unlikely(tsk->pid == 1))
		if (unlikely(tsk == child_reaper))
		panic("Attempted to kill init!");

		if (unlikely(current->ptrace & PT_TRACE_EXIT)) {

kernel/signal.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1990,7 +1990,7 @@ relock:
		continue;

		/* Init gets no signals it doesn't want. */
		if (current->pid == 1)
		if (current == child_reaper)
		continue;

		if (sig_kernel_stop(signr)) {

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