Date: Mon, 27 Nov 2017 16:52:21 -0800 From: Kees Cook <keescook@...omium.org> To: "Tobin C. Harding" <me@...in.cc> Cc: kernel-hardening@...ts.openwall.com, LKML <linux-kernel@...r.kernel.org>, Network Development <netdev@...r.kernel.org>, Steven Rostedt <rostedt@...dmis.org>, Tycho Andersen <tycho@...ho.ws> Subject: Re: [RFC 0/3] kallsyms: don't leak address when printing symbol On Mon, Nov 27, 2017 at 2:30 PM, Tobin C. Harding <me@...in.cc> wrote: > This is an RFC for two reasons. > > 1) I don't know who this patch set may break? > 2) Patch set includes a function that is not called. Function is there > to facilitate fixing breakages. > > _If_ no one gets broken then we can remove the unused function. > > Thanks for looking at this. > > 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 > potentially leaks kernel addresses. We could instead print something > _safe_. If kallsyms is made to return an error then callers of > sprint_symbol() can decide what to do. > > In the case of vsprintf we can print '<no-symbol>' (patch 2). > > In the case of trace we want the address so we can check the return code > and print the address if no symbol is found (patch 3). > > Design for this set loosely suggested by Steve Rostedt (so as not to > break ftrace). If tracing is the only place this is needed, this series seems reasonable to me. -Kees > > > Patch 1 and 2 tested, patch 3 (trace stuff) untested :) > > thanks, > Tobin. > > Tobin C. Harding (3): > kallsyms: don't leak address when symbol not found > vsprintf: print <no-symbol> if symbol not found > trace: print address if symbol not found > > include/linux/kernel.h | 2 ++ > kernel/kallsyms.c | 6 ++++-- > kernel/trace/trace.h | 24 ++++++++++++++++++++++++ > kernel/trace/trace_events_hist.c | 6 +++--- > lib/vsprintf.c | 18 +++++++++++++++--- > 5 files changed, 48 insertions(+), 8 deletions(-) > > -- > 2.7.4 > -- Kees Cook Pixel Security
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