linux-kernel - Re: lots of suspicious RCU traces

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]

Message-ID: <20121024180608.GA22840@redhat.com>
Date:	Wed, 24 Oct 2012 20:06:08 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Dave Jones <davej@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	linux-kernel@...r.kernel.org
Subject: Re: lots of suspicious RCU traces

On 10/24, Sergey Senozhatsky wrote:
>
> small question,
>
> ptrace_notify() and forward calls are able to both indirectly and directly call schedule(),
> /* direct call from ptrace_stop()*/,
> should, in this case, rcu_user_enter() be called before tracehook_report_syscall_exit(regs, step)
> and ptrace chain?

Well, I don't really understand this magic... but why?

Until we return to user-mode this CPU should be in "in_user = false" state.

I am not sure I understand how it is guaranteed that rcu_user_exit() was
called... probably TIF_NOHZ should trigger the slow path and ensure that
syscall_trace_enter()->rcu_user_exit() will be called.

Oleg.

--
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/