linux-kernel - Re: [PATCH -mm 0/3] ptrace: detach wakeup fixes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sun,  8 Feb 2009 16:54:05 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm 0/3] ptrace: detach wakeup fixes

> Q: when the tracer exits we bypass ptrace_disable() and
> clear_tsk_thread_flag(TIF_SYSCALL_TRACE), is this correct?

It's always been that way.  It's obviously wrong in an abstract sense.  But
for me, ptrace today is purely about compatibility with how it's behaved in
the past, however stupid that was--whenever it's been fully consistent and
predictable, userland is already saddled with coping with the stupidity.

> Perhaps we should move this code into __ptrace_unlink?

Locking nightmare.  ptrace_disable can do stuff that may require the thread
to be stopped like other ptrace operations require (fiddle registers),
might include access_process_vm, etc.  Trust me, we don't want to go there
now.  (In case you were looking for reasons why I'll be soon advocating
reorganization to get ptrace entirely out of the tasklist_lock arena, this
is a fine example of the true horror that the current data structure set-up
gives us.)

Thanks,
Roland
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/