linux-kernel - Re: [PATCH] Revert "x86/module: Detect and skip invalid relocations"

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Date:   Thu, 20 Jun 2019 10:33:31 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Cheng Jian <cj.chengjian@...wei.com>
cc:     linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
        jpoimboe@...hat.com, tglx@...utronix.de, mingo@...hat.com,
        huawei.libin@...wei.com, xiexiuqi@...wei.com,
        yangyingliang@...wei.com, bobo.shaobowang@...wei.com
Subject: Re: [PATCH] Revert "x86/module: Detect and skip invalid
 relocations"

On Thu, 20 Jun 2019, Cheng Jian wrote:

> This reverts commit eda9cec4c9a12208a6f69fbe68f72a6311d50032.
> 
> Since commit (eda9cec4c9a1 'x86/module: Detect and skip invalid
> relocations') add some sanity check in apply_relocate_add, borke
> re-insmod a kernel module which has been patched before,
> 
> The relocation informations of the livepatch module have been
> overwritten since first patched, so if we rmmod and insmod the
> kernel module, these values are not zero anymore, when
> klp_module_coming doing, and that commit marks them as invalid
> invalid_relocation.
> 
> Then the following error occurs:
> 
> 	module: x86/modules: Skipping invalid relocation target, existing value is nonzero for type 2, loc (____ptrval____), val ffffffffc000236c
> 	livepatch: failed to initialize patch 'livepatch_0001_test' for module 'test' (-8)
> 	livepatch: patch 'livepatch_0001_test' failed for module 'test', refusing to load module 'test'

Oh yeah. First reported here 20180602161151.apuhs2dygsexmcg2@...ble (LP ML 
only and there is no archive on lore.kernel.org yet. Sorry about that.). I 
posted v1 here 
https://lore.kernel.org/lkml/20180607092949.1706-1-mbenes@suse.cz/ and 
even started to work on v2 in March with arch-specific nullifying, but 
then I got sidetracked again. I'll move it up my todo list a bit.

Miroslav