[Latest Git kernel/Linux-next kernel] Xorg doesn't start after the seccomp updates v5.9-rc1

Hello,

Xorg doesn't start with the latest Git kernel anymore on some Linux 
distributions after the seccomp updates v5.9-rc1 [1]. For example on 
Fienix (Debian Sid PowerPC 32-bit) and on ubuntu MATE 16.04.6 (PowerPC 
32-bit). I tested these distributions on the A-EON AmigaOne X1000 [2], 
A-EON AmigaOne X5000 [3], and in a virtual e5500 QEMU machine with a 
virtio_gpu.

Error messages:

systemd-journald[2238]: Failed to send WATCHDOG-1 notification message: 
Connection refused
systemd-journald[2238]: Failed to send WATCHDOG-1 notification message: 
Transport endpoint is not connected
systemd-journald[2238]: Failed to send WATCHDOG-1 notification message: 
Transport endpoint is not connected
systemd-journald[2238]: Failed to send WATCHDOG-1 notification message: 
Transport endpoint is not connected
systemd-journald[2238]: Failed to send WATCHDOG-1 notification message: 
Transport endpoint is not connected
systemd-journald[2238]: Failed to send WATCHDOG-1 notification message: 
Transport endpoint is not connected

---

But Xorg works on Ubuntu 10.04.4 (PowerPC 32-bit), openSUSE Tumbleweed 
20190722 PPC64 and on Fedora 27 PPC64 with the latest Git kernel.

I bisected today [4].

Result: net/scm: Regularize compat handling of scm_detach_fds() 
(c0029de50982c1fb215330a5f9d433cec0cfd8cc) [5] is the first bad commit.

This commit has been merged with the seccomp updates v5.9-rc1 on 
2020-08-04 14:11:08 -0700 [1]. Since these updates, Xorg doesn't start 
anymore on some Linux distributions.

Unfortunately I wasn't able to revert the first bad commit. The first 
bad commit depends on many other commits, which unfortunately I don't 
know. I tried to remove the modifications of the files from the first 
bad commit but without any success. There are just too many dependencies.

Additionally I compiled a linux-next kernel because of the issue with 
the lastest Git kernel. Unfortunately this kernel doesn't boot. It can't 
initialize the graphics card.

Could you please test Xorg with the latest Git kernel on some Linux 
distributions?

Thanks,
Christian


[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9ecc6ea491f0c0531ad81ef9466284df260b2227
[2] https://en.wikipedia.org/wiki/AmigaOne_X1000
[3] http://wiki.amiga.org/index.php?title=X5000
[4] https://forum.hyperion-entertainment.com/viewtopic.php?p=51317#p51317
[5] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c0029de50982c1fb215330a5f9d433cec0cfd8cc

On Fri, Aug 07, 2020 at 04:45:14PM +0200, Christian Zigotzky wrote:

But Xorg works on Ubuntu 10.04.4 (PowerPC 32-bit), openSUSE Tumbleweed
20190722 PPC64 and on Fedora 27 PPC64 with the latest Git kernel.

I bisected today [4].

Result: net/scm: Regularize compat handling of scm_detach_fds()
(c0029de50982c1fb215330a5f9d433cec0cfd8cc) [5] is the first bad commit.

This commit has been merged with the seccomp updates v5.9-rc1 on 2020-08-04
14:11:08 -0700 [1]. Since these updates, Xorg doesn't start anymore on some
Linux distributions.

Hi! Thanks for bisecting; yes, sorry for the trouble (I'm still trying
to understand why my compat tests _passed_...). Regardless, can you try
this patch:

https://lore.kernel.org/lkml/20200807173609.GJ4402@mussarela/

-- 
Kees Cook

Hi Kees,

Thanks a lot for your patch! I think your patch works because I can patch the Git source code but the kernel doesn’t boot. In my point of view your modifications aren’t responsible for this second issue. The kernel can’t initialize the graphics card anymore. I think the latest DRM updates are responsible for the second issue. Because of this second issue I can’t test your patch.

Please test the latest Git kernel.

Thanks,
Christian

On 7. Aug 2020, at 19:45, Kees Cook [off-list ref] wrote:

On Fri, Aug 07, 2020 at 04:45:14PM +0200, Christian Zigotzky wrote:

quoted

But Xorg works on Ubuntu 10.04.4 (PowerPC 32-bit), openSUSE Tumbleweed
20190722 PPC64 and on Fedora 27 PPC64 with the latest Git kernel.

I bisected today [4].

Result: net/scm: Regularize compat handling of scm_detach_fds()
(c0029de50982c1fb215330a5f9d433cec0cfd8cc) [5] is the first bad commit.

This commit has been merged with the seccomp updates v5.9-rc1 on 2020-08-04
14:11:08 -0700 [1]. Since these updates, Xorg doesn't start anymore on some
Linux distributions.

Hi! Thanks for bisecting; yes, sorry for the trouble (I'm still trying
to understand why my compat tests _passed_...). Regardless, can you try
this patch:

https://lore.kernel.org/lkml/20200807173609.GJ4402@mussarela/

-- 
Kees Cook