linux-kernel - Re: [PATCH] kallsyms: don't leak address when printing symbol

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Message-ID: <20171109042318.GB775@jagdpanzerIV>
Date:   Thu, 9 Nov 2017 13:23:18 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     "Tobin C. Harding" <me@...in.cc>,
        kernel-hardening@...ts.openwall.com,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Theodore Ts'o <tytso@....edu>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Tycho Andersen <tycho@...ker.com>,
        "Roberts, William C" <william.c.roberts@...el.com>,
        Tejun Heo <tj@...nel.org>,
        Jordan Glover <Golden_Miller83@...tonmail.ch>,
        Greg KH <gregkh@...uxfoundation.org>,
        Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>,
        Ian Campbell <ijc@...lion.org.uk>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <wil.deacon@....com>,
        Chris Fries <cfries@...gle.com>,
        Dave Weinstein <olorin@...gle.com>,
        Daniel Micay <danielmicay@...il.com>,
        Djalal Harouni <tixxdz@...il.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        David Miller <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kallsyms: don't leak address when printing symbol

On (11/08/17 22:35), Steven Rostedt wrote:
> On Thu,  9 Nov 2017 12:50:29 +1100
> "Tobin C. Harding" <me@...in.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