linux-stable.git/kernel/ptrace.c, branch linux-2.6.30.y

ptrace: revert "ptrace_detach: the wrong wakeup breaks the ERESTARTxxx logic"

2009-06-05T01:07:40+00:00

Commit 95a3540da9c81a5987be810e1d9a83640a366bd5 ("ptrace_detach: the wrong
wakeup breaks the ERESTARTxxx logic") removed the "extra"
wake_up_process() from ptrace_detach(), but as Jan pointed out this breaks
the compatibility.

I believe the changelog is right and this wake_up() is wrong in many
ways, but GDB assumes that ptrace(PTRACE_DETACH, child, 0, 0) always
wakes up the tracee.

Despite the fact this breaks SIGNAL_STOP_STOPPED/group_stop_count logic,
and despite the fact this wake_up_process() can break another
assumption: PTRACE_DETACH with SIGSTOP should leave the tracee in
TASK_STOPPED case.  Because the untraced child can dequeue SIGSTOP and
call do_signal_stop() before ptrace_detach() calls wake_up_process().

Revert this change for now.  We need some fixes even if we we want to keep
the current behaviour, but these fixes are not for 2.6.30.

Signed-off-by: Oleg Nesterov 
Acked-by: Roland McGrath 
Cc: Jan Kratochvil 
Cc: Denys Vlasenko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ptrace: ptrace_attach: fix the usage of ->cred_exec_mutex

2009-04-27T10:30:51+00:00

ptrace_attach() needs task->cred_exec_mutex, not current->cred_exec_mutex.

Signed-off-by: Oleg Nesterov 
Acked-by: Roland McGrath 
Acked-by: David Howells 
Signed-off-by: James Morris

ptrace: fix exit_ptrace() vs ptrace_traceme() race

2009-04-13T22:04:31+00:00

Pointed out by Roland.  The bug was recently introduced by me in
"forget_original_parent: split out the un-ptrace part", commit
39c626ae47c469abdfd30c6e42eff884931380d6.

Since that patch we have a window after exit_ptrace() drops tasklist and
before forget_original_parent() takes it again.  In this window the child
can do ptrace(PTRACE_TRACEME) and nobody can untrace this child after
that.

Change ptrace_traceme() to not attach to the exiting ->real_parent.  We
don't report the error in this case, we pretend we attach right before
->real_parent calls exit_ptrace() which should untrace us anyway.

Signed-off-by: Oleg Nesterov 
Acked-by: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ptrace: some checkpatch fixes

2009-04-08T17:21:44+00:00

This fixes all the checkpatch --file complaints about kernel/ptrace.c
and also removes an unused #include.  I've verified that there are no
changes to the compiled code on x86_64.

Signed-off-by: Roland McGrath 
[ Removed the parts that just split a line  - Linus ]
Signed-off-by: Linus Torvalds

Merge branch 'core-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2009-04-04T00:35:06+00:00

* 'core-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  ptrace: remove a useless goto

ptrace_untrace: fix the SIGNAL_STOP_STOPPED check

2009-04-03T02:05:00+00:00

This bug is ancient too. ptrace_untrace() must not resume the task
if the group stop in progress, we should set TASK_STOPPED instead.

Unfortunately, we still have problems here:

	- if the process/thread was traced, SIGNAL_STOP_STOPPED
	  does not necessary means this thread group is stopped.

	- ptrace breaks the bookkeeping of ->group_stop_count.

Signed-off-by: Oleg Nesterov 
Cc: Jerome Marchand 
Cc: Roland McGrath 
Cc: Denys Vlasenko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ptrace_detach: the wrong wakeup breaks the ERESTARTxxx logic

2009-04-03T02:05:00+00:00

Another ancient bug. Consider this trivial test-case,

	int main(void)
	{
		int pid = fork();

		if (pid) {
			ptrace(PTRACE_ATTACH, pid, NULL, NULL);
			wait(NULL);
			ptrace(PTRACE_DETACH, pid, NULL, NULL);
		} else {
			pause();
			printf("WE HAVE A KERNEL BUG!!!\n");
		}

		return 0;
	}

the child must not "escape" for sys_pause(), but it can and this was seen
in practice.

This is because ptrace_detach does:

	if (!child->exit_state)
		wake_up_process(child);

this wakeup can happen after this child has already restarted sys_pause(),
because it gets another wakeup from ptrace_untrace().

With or without this patch, perhaps sys_pause() needs a fix.  But this
wakeup also breaks the SIGNAL_STOP_STOPPED logic in ptrace_untrace().

Remove this wakeup.  The caller saw this task in TASK_TRACED state, and
unless it was SIGKILL'ed in between __ptrace_unlink()->ptrace_untrace()
should handle this case correctly.  If it was SIGKILL'ed, we don't need to
wakup the dying tracee too.

Signed-off-by: Oleg Nesterov 
Cc: Jerome Marchand 
Acked-by: Roland McGrath 
Cc: Denys Vlasenko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

forget_original_parent: split out the un-ptrace part

2009-04-03T02:05:00+00:00

By discussion with Roland.

- Rename ptrace_exit() to exit_ptrace(), and change it to do all the
  necessary work with ->ptraced list by its own.

- Move this code from exit.c to ptrace.c

- Update the comment in ptrace_detach() to explain the rechecking of
  the child->ptrace.

Signed-off-by: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Cc: "Metzger, Markus T" 
Cc: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ptrace: fix possible zombie leak on PTRACE_DETACH

2009-04-03T02:04:59+00:00

When ptrace_detach() takes tasklist, the tracee can be SIGKILL'ed.  If it
has already passed exit_notify() we can leak a zombie, because a) ptracing
disables the auto-reaping logic, and b) ->real_parent was not notified
about the child's death.

ptrace_detach() should follow the ptrace_exit's logic, change the code
accordingly.

Signed-off-by: Oleg Nesterov 
Cc: Jerome Marchand 
Cc: Roland McGrath 
Tested-by: Denys Vlasenko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ptrace: kill __ptrace_detach(), fix ->exit_state check

2009-04-03T02:04:59+00:00

Move the code from __ptrace_detach() to its single caller and kill this
helper.

Also, fix the ->exit_state check, we shouldn't wake up EXIT_DEAD tasks.
Actually, I think task_is_stopped_or_traced() makes more sense, but this
needs another patch.

Signed-off-by: Oleg Nesterov 
Cc: Jerome Marchand 
Cc: Roland McGrath 
Cc: Denys Vlasenko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds