Messages in this thread | | | Date | Fri, 4 Sep 2009 14:46:04 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/1] exec: do not sleep in TASK_TRACED under ->cred_guard_mutex |
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On 09/04, David Howells wrote: > > Oleg Nesterov <oleg@redhat.com> 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... correctly.
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.
Oleg.
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