Re: [PATCH 1/1] exec: do not sleep in TASK_TRACED under->cred_guard_mutex

From: Oleg Nesterov
Date: Fri Sep 04 2009 - 08:52:21 EST

On 09/04, David Howells wrote:
> Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> > But I strongly believe we should blame another patch
> >
> > "CRED: Make execve() take advantage of copy-on-write credentials"
> > a6f76f23d297f70e2a6b3ec607f7aeeea9e37e8d
> >
> > The tracee must not sleep in TASK_TRACED holding this mutex (it was named
> > cred_exec_mutex). Even if we remove ->cred_guard_mutex from mm_for_maps()
> > and proc_pid_attr_write(), another task doing PTRACE_ATTACH should not
> > hang until it is killed or the tracee resumes.

(Argh. Sorry David, the changelog should have mentioned tracehook_report_exec()
more explicitely).

So, David, do you agree with this patch? Do you think it can go to 2.6.31 ?

> Btw, should mm_for_maps() use mutex_lock_interruptible()? There doesn't seem
> any point making it non-interruptible (except for kill signals) - unless that
> would muck up seqfile handling.

Perhaps, but we should change m_start() first, it should check IS_ERR() instead
of mm != NULL. Afaics, vfs_read()->seq_read() path will return ERESTART...

I am not sure would be right though, short reads can confuse user space. And
this can't solve the problem, this only helps to react to signals.


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at