linux-kernel - Re: [PATCH] module: Harden STRICT_MODULE

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: <alpine.LSU.2.21.2004061146590.26870@pobox.suse.cz>
Date:   Mon, 6 Apr 2020 11:55:39 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
cc:     Peter Zijlstra <peterz@...radead.org>, jeyu@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        keescook@...omium.org
Subject: Re: [PATCH] module: Harden STRICT_MODULE_RWX

On Fri, 3 Apr 2020, Josh Poimboeuf wrote:

> On Fri, Apr 03, 2020 at 06:37:16PM +0200, Peter Zijlstra wrote:
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < hdr->e_shnum; i++) {
> > +		if (sechdrs[i].sh_flags & (SHF_EXECINSTR|SHF_WRITE))
> > +			return -ENOEXEC;
> 
> I think you only want the error when both are set?
> 
> 		if (sechdrs[i].sh_flags & (SHF_EXECINSTR|SHF_WRITE) == (SHF_EXECINSTR|SHF_WRITE))

A section with SHF_EXECINSTR and SHF_WRITE but without SHF_ALLOC would be 
strange though, no? It wouldn't be copied to the final module later 
anyway.

Looking at layout_sections()... a section with 
SHF_EXECINSTR|SHF_WRITE|SHF_ALLOC would not be counted at all. However, 
move_module() later copies everything with SHF_ALLOC flag to the final 
module. If there is WXA section, there would be a bug because the 
allocation there would not get the correct size. In that case it is 
important to error out early as you're proposing.

Am I missing something?

Miroslav