Re: Warnings and errors in drm_mode_config_cleanup when booting 6.19.10 and 7.0-rc5

[Thorsten Leemhuis <regressions@leemhuis.info>]

[CCing Sasha]

On 4/6/26 10:17, Greg KH wrote:
> On Mon, Apr 06, 2026 at 03:54:39AM -0400, Matt Fagnani wrote:
>> On 2026-04-02 08:12, Greg KH wrote:
>>> On Sat, Mar 28, 2026 at 11:52:48AM +0100, Thorsten Leemhuis wrote:
>>>> On 3/28/26 11:30, Matt Fagnani wrote:
>>>>> I could try to bisect. The commit
>>>>> e493c135980f90c20308d1a98f2e0d1223951e94 drm: Fix use-after-free on
>>>>> framebuffers and property blobs when calling drm_dev_unplug was included
>>>>> in 6.19.10 and changed drm_mode_config_cleanup https://git.kernel.org/
>>>>> pub/scm/linux/kernel/git/stable/linux.git/commit/?
>>>>> h=linux-6.19.y&id=e493c135980f90c20308d1a98f2e0d1223951e94
>>>> Did a quick search. Turns out this is mainline commit 6bee098b914176
>>>> ("drm: Fix use-after-free on framebuffers and property blobs when
>>>> calling drm_dev_unplug") [...] is turns out that is in the
>>>> process of getting reverted:
>>>>
>>>> See https://lore.kernel.org/all/20260326082217.39941-2-dev@lankhorst.se/
>>>> or 45ebe43ea00d6b ("Revert "drm: Fix use-after-free on framebuffers and
>>>> property blobs when calling drm_dev_unplug"") [next-20260327
>>>> (pending-fixes)].
>>>> Sasha and Greg: you might want to make sure to pick this up.
>>> When it shows up in a Linus-released kernel, can someone remind us?
>> 7.0-rc7 https://lwn.net/Articles/1066405/ had the patch Revert "drm: Fix
>> use-after-free on framebuffers and property blobs when calling
>> drm_dev_unplug" https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v7.0-rc7&id=45ebe43ea00d6b9f5b3e0db9c35b8ca2a96b7e70 Thanks.
> 
> Does not apply on 6.6.y or 6.1.y, so can someone provide a working
> backport for those branches?

Hmm, those two got manual backports Sasha did, so he might be in the
best position to submit the reverts, too.

But to save you two a few cycles I just prepared those reverts and will
submit them in reply to this mail. Handle with care, as they are
untested. Not really sure if this was a wise idea at all. In case of
problems it might be the best if one of you could redo them from scratch
in case you have scripts to handle situations like these.

Ciao. Thorsten