linux-kernel - Re: [PATCH v2] livepatch: x86: make kASLR logic more accurate

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Message-ID: <alpine.LNX.2.00.1504252239150.16113@pobox.suse.cz>
Date:	Sat, 25 Apr 2015 22:39:48 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
cc:	Seth Jennings <sjenning@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] livepatch: x86: make kASLR logic more accurate

On Fri, 24 Apr 2015, Josh Poimboeuf wrote:

> >  #if defined(CONFIG_RANDOMIZE_BASE)
> > -	/* KASLR is enabled, disregard old_addr from user */
> > -	func->old_addr = 0;
> > +	/* If KASLR has been enabled, adjust old_addr accordingly */
> > +	if (kaslr_enabled())
> > +		func->old_addr += klp_vmlinux_relocation_offset();
> 
> The old_addr field is optional, where a value of 0 means "lookup the
> address in kallsyms".  So its value should only be adjusted if old_addr
> is already non-zero.  Otherwise the zero value will be replaced with a
> bad address and it will mistakenly call klp_verify_vmlinux_symbol() with
> the bad address instead of klp_find_object_symbol().

Fair enough, good point, will take this into account in v3. Thanks,

-- 
Jiri Kosina
SUSE Labs
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