linux-kernel - Re: [PATCH v2 15/39] x86/ibt,kprobes: Fix more +0 assumptions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Yh3ZQQv8GjtqgUF4@hirez.programming.kicks-ass.net>
Date:   Tue, 1 Mar 2022 09:28:49 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     x86@...nel.org, joao@...rdrivepizza.com, hjl.tools@...il.com,
        jpoimboe@...hat.com, andrew.cooper3@...rix.com,
        linux-kernel@...r.kernel.org, ndesaulniers@...gle.com,
        keescook@...omium.org, samitolvanen@...gle.com,
        mark.rutland@....com, alyssa.milburn@...el.com, mbenes@...e.cz,
        rostedt@...dmis.org, alexei.starovoitov@...il.com,
        naveen.n.rao@...ux.vnet.ibm.com
Subject: Re: [PATCH v2 15/39] x86/ibt,kprobes: Fix more +0 assumptions

On Tue, Mar 01, 2022 at 11:49:05AM +0900, Masami Hiramatsu wrote:
> > +static kprobe_opcode_t *
> > +_kprobe_addr(kprobe_opcode_t *addr, const char *symbol_name,
> > +	     unsigned long offset, bool *on_func_entry)
> >  {
> >  	if ((symbol_name && addr) || (!symbol_name && !addr))
> >  		goto invalid;
> >  
> >  	if (symbol_name) {
> > +		/*
> > +		 * Input: @sym + @offset
> > +		 * Output: @addr + @offset
> > +		 *
> > +		 * NOTE: kprobe_lookup_name() does *NOT* fold the offset
> > +		 *       argument into it's output!
> > +		 */
> >  		addr = kprobe_lookup_name(symbol_name, offset);
> 
> Hmm, there are 2 issues.
> 
> - the 'addr' includes the 'offset' here.

AFAICT it doesn't (I ever wrote that in the comment on top). There's two
implementations of kprobe_lookup_name(), the weak version doesn't even
use the offset argument, and the PowerPC implementation only checks for
!offset and doesn't fold it.

> - the 'offset' is NOT limited under the symbol size.
>   (e.g. symbol_name = "_text" and @offset points the offset of target symbol from _text)
> 
> This means we need to call kallsyms_lookup_size_offset() in this case too.

I'm feeling we should error out in that case. Using sym+offset beyond
the limits of sym is just daft.

But if you really want/need to retain that, then yes, we need that
else branch unconditionally :/