From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [PATCH] kallsyms: don't leak address when printing symbol
Date: Thu, 9 Nov 2017 13:23:18 +0900
Message-ID: <20171109042318.GB775@jagdpanzerIV>
References: <1510192229-20038-1-git-send-email-me@tobin.cc>
 <20171108223555.52c01531@vmware.local.home>
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Cc: "Tobin C. Harding" <me@tobin.cc>,
        kernel-hardening@lists.openwall.com,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Theodore Ts'o <tytso@mit.edu>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Tycho Andersen <tycho@docker.com>,
        "Roberts, William C" <william.c.roberts@intel.com>,
        Tejun Heo <tj@kernel.org>,
        Jordan Glover <Golden_Miller83@protonmail.ch>,
        Greg KH <gregkh@linuxfoundation.org>,
        Petr Mladek <pmladek@suse.com>, Joe Perches <joe@perches.com>,
        Ian Campbell <ijc@hellion.org.uk>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <wil.deacon@arm.com>,
        Chris Fries <cfries@google.com>,
        Dave Weinstein <olorin@google.co
To: Steven Rostedt <rostedt@goodmis.org>
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On (11/08/17 22:35), Steven Rostedt wrote:
> On Thu,  9 Nov 2017 12:50:29 +1100
> "Tobin C. Harding" <me@tobin.cc> wrote:
> 
> > Currently if a pointer is printed using %p[ssB] and the symbol is not
> > found (kallsyms_lookup() fails) then we print the actual address. This
> > leaks kernel addresses. We should instead print something _safe_.
> > 
> > Print "<no-symbol>" instead of kernel address.
> 
> Ug, ftrace requires this to work as is, as it uses it to print some
> addresses that may or may not be a symbol.
> 
> If anything, can this return a success or failure if it were to find a
> symbol or not, and then something like ftrace could decide to use %x if
> it does not.
> 
> And yes, ftrace leaks kernel addresses all over the place, that's just
> the nature of tracing the kernel.
> 

agree, I kinda suspect that that "0x%lx" sometimes can be useful.
at least one can tell if the frame is from modules or kernel, and
objdump it may be.

	-ss