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authorEric W. Biederman <ebiederm@xmission.com>2006-04-14 04:05:55 -0600
committerLinus Torvalds <torvalds@g5.osdl.org>2006-04-14 08:49:19 -0700
commitc06511d12d720b23c8dffff23004f0a888698f20 (patch)
tree96916946cd8374821b10316c8f5fabc4917a38d6 /fs/exec.c
parent0e5e24bf64b755a034d8294303bc61d8f40ebeaf (diff)
downloadop-kernel-dev-c06511d12d720b23c8dffff23004f0a888698f20.zip
op-kernel-dev-c06511d12d720b23c8dffff23004f0a888698f20.tar.gz
[PATCH] de_thread: Don't change our parents and ptrace flags.
This is two distinct changes. - Not changing our real parents. - Not changing our ptrace parents. Not changing our real parents is trivially correct because both tasks have the same real parents as they are part of a thread group. Now that we demote the leader to a thread there is no longer any reason to change it's parentage. Not changing our ptrace parents is a user visible change if someone looks hard enough. I don't think user space applications will care or even notice. In the practical and I think common case a debugger will have attached to all of the threads using the same ptrace flags. From my quick skim of strace and gdb that appears to be the case. Which if true means debuggers will not notice a change. Before this point we have already generated a ptrace event in do_exit that reports the leaders pid has died so de_thread is visible to a debugger. Which means attempting to hide this case by copying flags around appears excessive. By not doing anything it avoids all of the weird locking issues between de_thread and ptrace attach, and removes one case from consideration for fixing the ptrace locking. This only addresses Oleg's first concern with ptrace_attach, that of the problems caused by reparenting. Oleg's second concern is essentially a race between ptrace_attach and release_task that causes an oops when we get to force_sig_specific. There is nothing special about de_thread with respect to that race. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/exec.c')
-rw-r--r--fs/exec.c27
1 files changed, 0 insertions, 27 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 3234a0c..4121bb5 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -665,9 +665,7 @@ static int de_thread(struct task_struct *tsk)
* and to assume its PID:
*/
if (!thread_group_leader(current)) {
- struct task_struct *parent;
struct dentry *proc_dentry1, *proc_dentry2;
- unsigned long ptrace;
/*
* Wait for the thread group leader to be a zombie.
@@ -704,22 +702,6 @@ static int de_thread(struct task_struct *tsk)
* two threads with a switched PID, and release
* the former thread group leader:
*/
- ptrace = leader->ptrace;
- parent = leader->parent;
- if (unlikely(ptrace) && unlikely(parent == current)) {
- /*
- * Joker was ptracing his own group leader,
- * and now he wants to be his own parent!
- * We can't have that.
- */
- ptrace = 0;
- }
-
- ptrace_unlink(current);
- ptrace_unlink(leader);
- remove_parent(current);
- remove_parent(leader);
-
/* Become a process group leader with the old leader's pid.
* Note: The old leader also uses thispid until release_task
@@ -732,8 +714,6 @@ static int de_thread(struct task_struct *tsk)
attach_pid(current, PIDTYPE_SID, current->signal->session);
list_add_tail(&current->tasks, &init_task.tasks);
- current->parent = current->real_parent = leader->real_parent;
- leader->parent = leader->real_parent = child_reaper;
current->group_leader = current;
leader->group_leader = current;
@@ -742,13 +722,6 @@ static int de_thread(struct task_struct *tsk)
detach_pid(leader, PIDTYPE_SID);
list_del_init(&leader->tasks);
- add_parent(current);
- add_parent(leader);
- if (ptrace) {
- current->ptrace = ptrace;
- __ptrace_link(current, parent);
- }
-
current->exit_signal = SIGCHLD;
BUG_ON(leader->exit_state != EXIT_ZOMBIE);
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