linux-kernel - Re: [PATCH v2 7/9] x86/module: Use text

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: <20200417145136.ls3tafthtql6prhn@treble>
Date:   Fri, 17 Apr 2020 09:51:36 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jessica Yu <jeyu@...nel.org>, x86@...nel.org
Subject: Re: [PATCH v2 7/9] x86/module: Use text_poke() for late relocations

On Fri, Apr 17, 2020 at 04:29:44PM +0200, Peter Zijlstra wrote:
> On Fri, Apr 17, 2020 at 09:04:32AM -0500, Josh Poimboeuf wrote:
> > +int apply_relocate_add(Elf64_Shdr *sechdrs,
> > +		   const char *strtab,
> > +		   unsigned int symindex,
> > +		   unsigned int relsec,
> > +		   struct module *me)
> > +{
> > +	int ret;
> > +	bool early = me->state == MODULE_STATE_UNFORMED;
> > +	void *(*write)(void *, const void *, size_t) = memcpy;
> > +
> > +	if (!early) {
> > +		write = text_poke;
> > +		mutex_lock(&text_mutex);
> > +	}
> > +
> > +	ret = __apply_relocate_add(sechdrs, strtab, symindex, relsec, me,
> > +				   write);
> > +
> > +	if (!early) {
> > +		mutex_unlock(&text_mutex);
> > +		text_poke_sync();
> 
> I'm thinking text_poke_sync() wants to be inside text_mutex. Although
> given that nothing should be running that text, it really doesn't
> matter.

Yeah, makes sense.

diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index 2a997afa04c6..23c95a53d20e 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -237,8 +237,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
 				   write);
 
 	if (!early) {
-		mutex_unlock(&text_mutex);
 		text_poke_sync();
+		mutex_unlock(&text_mutex);
 	}
 
 	return ret;