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From: Steven Rostedt <rostedt@goodmis.org>
To: Kees Cook <keescook@chromium.org>
Cc: Jann Horn <jannh@google.com>, Ingo Molnar <mingo@kernel.org>,
	Cong Wang <xiyou.wangcong@gmail.com>,
	Qitao Xu <qitao.xu@bytedance.com>,
	"David S. Miller" <davem@davemloft.net>,
	Network Development <netdev@vger.kernel.org>,
	Cong Wang <cong.wang@bytedance.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-hardening@vger.kernel.org
Subject: Re: tracepoints and %p [was: Re: [Patch net-next resend v2] net: use %px to print skb address in trace_netif_receive_skb]
Date: Wed, 28 Jul 2021 16:41:03 -0400	[thread overview]
Message-ID: <20210728164103.245c9db4@oasis.local.home> (raw)
In-Reply-To: <202107281146.B2160202D@keescook>

On Wed, 28 Jul 2021 11:48:11 -0700
Kees Cook <keescook@chromium.org> wrote:

> > That is exactly what is happening. I wrote the following to the replied
> > text up at the top, then noticed you basically stated the same thing
> > here ;-)  
> 
> Where is the %px being formatted then? If it's the kernel itself (which
> is the only thing that does %px), then it doesn't need to be %px, since
> the raw data is separate. i.e. leave it %p for whatever logs will get
> spilled out to who knows where.

The trace events shown by tracefs/trace are formatted via the kernel
sprintf() and friends, which will hash "%p".

But the raw data read to trace-cmd (and other tools), uses
libtraceevent, that parses the printf-fmt of a trace event just like
the kernel does. But since we are already in user space, it is pretty
pointless to implement "%p" with hashing. But it does understand what
"%px" is.

> 
> How does ftrace interact with lockdown's confidentiality mode?
> 

as Jann replied. If you enable "LOCKDOWN_TRACEFS" you lose all access
to the tracing interface.

-- Steve

      parent reply	other threads:[~2021-07-28 20:41 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-15  5:59 [Patch net-next resend v2] net: use %px to print skb address in trace_netif_receive_skb Cong Wang
2021-07-15 17:40 ` patchwork-bot+netdevbpf
2021-07-23  7:09 ` Kees Cook
2021-07-28  3:17   ` Cong Wang
2021-07-28 15:13   ` tracepoints and %p [was: Re: [Patch net-next resend v2] net: use %px to print skb address in trace_netif_receive_skb] Jann Horn
2021-07-28 15:56     ` Steven Rostedt
2021-07-28 18:48       ` Kees Cook
2021-07-28 18:56         ` Jann Horn
2021-07-28 20:41         ` Steven Rostedt [this message]

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