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Commit fef23e7f authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Linus Torvalds
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[PATCH] exec: allow init to exec from any thread. 



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: default avatarEric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ca9ba447

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 @@ int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka, 
			continue;



		/* Init gets no signals it doesn't want.  */

		if (current->pid == 1)

		if (current == child_reaper)

			continue;



		if (sig_kernel_stop(signr)) {