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[PATCH] exec: allow init to exec from any thread.

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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>
This commit is contained in:
Eric W. Biederman 2006-03-28 16:10:58 -08:00 committed by Linus Torvalds
parent ca9ba4471c
commit fef23e7fbb
3 changed files with 14 additions and 3 deletions
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13
fs/exec.c
View file

@ -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();

2
kernel/exit.c
View file

@ -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)) {

2
kernel/signal.c
View file

@ -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)) {