Re: [PATCH 5.18 000/231] 5.18.13-rc1 review

Jiri Slaby
2022-07-21T06:08:01Z

On 21. 07. 22, 7:31, Jiri Slaby wrote:
> On 21. 07. 22, 0:00, Peter Zijlstra wrote:
>> On Wed, Jul 20, 2022 at 11:47:02PM +0200, Peter Zijlstra wrote:
>>> On Wed, Jul 20, 2022 at 12:57:26PM -0500, Justin Forbes wrote:
>>>> On Wed, Jul 20, 2022 at 10:28:33AM -0700, Linus Torvalds wrote:
>>>>> [ Adding PeterZ and Jiri to the participants. ]
>>>>>
>>>>> Looks like 5.18.13 added that commit 9bb2ec608a20 ("objtool: Update
>>>>> Retpoline validation") but I don't see 3131ef39fb03 ("x86/asm/32: Fix
>>>>> ANNOTATE_UNRET_SAFE use on 32-bit") in that list.
>>>>
>>>> It should be noted that the build doesn't fail, it just warns.
>>>> I am guessing the 32bit failure is what promoted someone to look at
>>>> the logs to begin with and notice the warn initially. I just verified
>>>> that it exists in our builds of 5.18.13-rc1, but not on mainline
>>>> builds.
>>>> I am gueesing it is because commit 9bb2ec608a20 ("objtool: Update
>>>> Retpoline
>>>> validation") should be followed up with at least commit f43b9876e857c
>>>> ("x86/retbleed: Add fine grained Kconfig knobs")
>>>
>>> Still updateing the stable repro to see what the actual code looks like,
>>> but that warning seems to suggest the -mfunction-return=thunk-extern
>>> compiler argument went missing.
>>>
>>> For all the files objtool complains about, does the V=1 build output
>>> show that option?
>>
>> Ok, I'm now looking at stable-rc/linux-5.18.y which reports itself as:
>>
>> VERSION = 5
>> PATCHLEVEL = 18
>> SUBLEVEL = 13
>> EXTRAVERSION = -rc1
>>
>> and I'm most terribly confused... it has the objtool patch to validate
>> return thunks, *however*, I'm not seeing any actual retbleed mitigations
>> *anywhere*.
>>
>> How, what, why!?
>
> They were all put aside until all this gets resolved. You can find them
> in the stable-queue tree:
> git://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git
>
> in retbleed-5.18/.

Ah, apparently not all, as you noted above. But this is obviously a mistake:
https://lore.kernel.org/all/YthbbBY4JumsBcHU@kroah.com/

> regards,--
--
js
suse labs