Kernel 6.5.0 with the parameter UBSAN disabled + Nvidia kernel version 535.129.03 = any kind of video flow (offline or online) is frozen at the beginning.

[Mario Marietto]

Hello.

I’ve upgraded Ubuntu 23.04 to 23.10 recently. On my Ubuntu 23.10 I’m using
kernel 6.5.0-10-generic and I’ve installed the nVidia driver version
535.129.03. (my nvidia gpu is the RTX 2080 ti ; my cpu is the intel I9). I
don't have exactly the same bug of this :


https://bugs.launchpad.net/ubuntu/+source/broadcom-sta/+bug/2030978?comments=all


because the error in the Ubuntu bug report is for a different kernel
module. But the underlying cause is probably the same.

Possibly the code for the nvidia-uvm module is designed for kernel versions
< 6.5, so when Ubuntu upgraded to Linux kernel 6.5, it broke some modules
because of changes to UBSAN in Linux 6.5 which causes modules such as
nvidia-uvm to need patches to be compatible with Linux 6.5, but either
nvidia has not yet provided a version of nvidia-uvm that is compatible with
Linux 6.5 or Ubuntu neglected to apply an updated version from nvidia that
is compatible with Linux 6.5.

I didn’t see this error on Ubuntu 23.04,maybe because it does not use the
kernel 6.5 by default,but 23.10 does.

I see a lot of those errors when I issue the command “dmesg” and any
audio-video streamings don’t flow.

At the beginning I've thought to revert the commit in 6.5 mentioned in the
bug report that caused a similar problem in the broadcom-wl module:


https://bugs.launchpad.net/ubuntu/+source/broadcom-sta/+bug/2030978


In there it mentions the commit in 6.5.y causing the trouble:



On Linux 6.5, due to commit 2d47c6956ab3 ("ubsan: Tighten UBSAN_BOUNDSon
GCC"), flexible trailing arrays declared like \whatever_t foo[1];\will
generate warnings when CONFIG_UBSAN & co. is enabled.


The commit is here:


https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-6.5.y&id=2d47c6956ab3c8b580a59d7704aab3e2a4882b6c


BUT I don't use a broadcom-wl,so I've disabled the UBSAN parameter and I've
recompiled and installed kernel 6.5.0 and the nvidia-driver worked fine :


https://pastebin.ubuntu.com/p/7DYsbJwNbT/


(It does not work with the kernel 6.5.3. But only with 6.5.0)


# uname -a
Linux Z390-AORUS-PRO-DEST 6.5.0 #1 SMP PREEMPT_DYNAMIC Tue Nov  7
16:26:55 CET 2023 x86_64 x86_64 x86_64 GNU/Linux


What's the problem now ?


Even if I have been able to fix the previous error,at the moment I can't
watch any video streaming,online or offline. Simply it does not flow at
all. Any kind of video flow is frozen at the beginning of the stream. I
took a look at the dmesg messages and I saw the ugly error that you see
below. Maybe it is correlated with the problem :


https://pastebin.ubuntu.com/p/SyhrqwKncZ/


What to do ?


*UPDATE :*

*I've discovered a very odd behavior. If I exclude the audio from the
video, the video stream moves on. If I keep the audio on, the video stream
freezes.*

-- 
Mario.
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