From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Kees Cook <keescook@chromium.org>,
Fengguang Wu <fengguang.wu@intel.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: yama_ptrace_access_check(): possible recursive locking detected
Date: Wed, 15 Aug 2012 19:56:51 +0200 [thread overview]
Message-ID: <20120815175651.GA17814@redhat.com> (raw)
In-Reply-To: <1345041021.31459.88.camel@twins>
On 08/15, Peter Zijlstra wrote:
>
> On Wed, 2012-08-15 at 15:01 +0200, Oleg Nesterov wrote:
> > BTW, set_task_comm()->wmb() and memset() should die. There are
> > not needed afaics, and the comment is misleading.
>
> As long as we guarantee there's always a terminating '\0',
Yes, but we already have this guarantee?
Unless of course some buggy code does something wrong with task->comm[],
but nobody should do this.
IOW, task->comm[TASK_COMM_LEN - 1] is always 0, no?
> now strlcpy()
> doesn't pad the result,
afaics set_task_comm()->strlcpy() doesn't change the last byte too.
> however if we initialize the ->comm to all 0s in
> fork()
fork() is special, yes. ->comm is copied by dup_task_struct() and
the new task_struct can have everything in ->comm. But nobody can
see the new task yet, and nobody can play with its ->comm.
Or I misunderstood?
> That barrier is indeed completely pointless as there's no pairing
> barrier anywhere.
Yes, agreed.
Oleg.
next prev parent reply other threads:[~2012-08-15 18:00 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-26 13:47 yama_ptrace_access_check(): possible recursive locking detected Fengguang Wu
2012-07-26 15:41 ` Oleg Nesterov
2012-07-30 17:00 ` Kees Cook
2012-08-10 1:39 ` Kees Cook
2012-08-10 1:52 ` Fengguang Wu
2012-08-14 21:16 ` Kees Cook
2012-08-15 3:01 ` Fengguang Wu
2012-08-15 5:56 ` Kees Cook
2012-08-15 8:05 ` Peter Zijlstra
2012-08-15 13:01 ` Oleg Nesterov
2012-08-15 14:30 ` Peter Zijlstra
2012-08-15 17:56 ` Oleg Nesterov [this message]
2012-08-15 18:09 ` Kees Cook
2012-08-15 18:17 ` Oleg Nesterov
2012-08-15 18:30 ` Kees Cook
2012-08-15 18:44 ` Alan Cox
2012-08-15 18:43 ` Kees Cook
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