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CLONE_PARENT shouldn't allow to set ->exit_signal

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The child must not control its ->exit_signal, it is the parent who
decides which signal the child should use for notification.

This means that CLONE_PARENT should not use "clone_flags & CSIGNAL",
the forking task is the sibling of the new process and their parent
doesn't control exit_signal in this case.

This patch uses ->exit_signal of the forking process, but perhaps
we should simply use SIGCHLD.

We read group_leader->exit_signal lockless, this can race with the
ORIGINAL_SIGNAL -> SIGCHLD transition, but this is fine.

Potentially this change allows to kill self_exec_id/parent_exec_id.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2012-03-14 19:55:38 +01:00 committed by Linus Torvalds
parent ed378a52da
commit 5f8aadd8b9
1 changed files with 7 additions and 1 deletions
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8
kernel/fork.c
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@ -1340,7 +1340,13 @@ static struct task_struct *copy_process(unsigned long clone_flags,
clear_all_latency_tracing(p);
/* ok, now we should be set up.. */
p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
if (clone_flags & CLONE_THREAD)
p->exit_signal = -1;
else if (clone_flags & CLONE_PARENT)
p->exit_signal = current->group_leader->exit_signal;
else
p->exit_signal = (clone_flags & CSIGNAL);
p->pdeath_signal = 0;
p->exit_state = 0;