All of lore.kernel.org
 help / color / mirror / Atom feed
From: Steven Rostedt <rostedt@goodmis.org>
To: David Laight <David.Laight@ACULAB.COM>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Pingfan Liu <kernelfans@gmail.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Tom Zanussi <zanussi@kernel.org>
Subject: Re: [PATCH v2] tracing: Add test for user space strings when filtering on  string pointers
Date: Mon, 10 Jan 2022 19:21:04 -0500	[thread overview]
Message-ID: <20220110192104.5daaabe7@gandalf.local.home> (raw)
In-Reply-To: <7c2789f990394df5b7907287fc0e1232@AcuMS.aculab.com>

On Mon, 10 Jan 2022 22:03:20 +0000
David Laight <David.Laight@ACULAB.COM> wrote:

> > Only root has access to the information read here. All tracing requires
> > root or those explicitly given access to the tracing data, which pretty
> > much allows all access to kernel internals (including all memory). So
> > nothing to worry about here ;-)  
> 
> Is this filtering trace using a filename passed to a system call by a user program?
> In which case a user program can set up a system call that normally fails
> (because the copy_from_user() errors) but if root tries to run a system
> call event trace on that process can read arbitrary addresses and
> thus crash the system?
> 
> While unlikely root might be persuaded to try to run the trace.

Yes. That's exactly what the code does today, and why it's a bug.

This patch instead uses copy_from_user_nofault/copy_from_kernel_nofault and
copies it into a temp buffer and then compares against that.

If a user passes in a crazy pointer, the copy_from_user/kernel_nofault()
will not read it, and the filter simply fails to match. Nothing bad will
happen.

-- Steve

  reply	other threads:[~2022-01-11  0:21 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-10 16:55 [PATCH v2] tracing: Add test for user space strings when filtering on string pointers Steven Rostedt
2022-01-10 17:11 ` David Laight
2022-01-10 17:24   ` Steven Rostedt
2022-01-10 17:29     ` Steven Rostedt
2022-01-10 21:58     ` David Laight
2022-01-11 20:55       ` Sven Schnelle
2022-01-13 17:57         ` Steven Rostedt
2022-01-13 21:28           ` Sven Schnelle
2022-01-13 21:51             ` Steven Rostedt
2022-01-14  2:15               ` Steven Rostedt
2022-01-14  7:29                 ` Sven Schnelle
2022-01-14  9:35                 ` David Laight
2022-01-13 22:11             ` David Laight
2022-01-13 22:28               ` Steven Rostedt
2022-01-10 22:03     ` David Laight
2022-01-11  0:21       ` Steven Rostedt [this message]
2022-01-12  4:13     ` Pingfan Liu
2022-01-13 18:04       ` Steven Rostedt
2022-01-13 22:02       ` Steven Rostedt

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20220110192104.5daaabe7@gandalf.local.home \
    --to=rostedt@goodmis.org \
    --cc=David.Laight@ACULAB.COM \
    --cc=akpm@linux-foundation.org \
    --cc=kernelfans@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mhiramat@kernel.org \
    --cc=mingo@kernel.org \
    --cc=zanussi@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.