Hello !

We have lengthily worked on this problem with a friend to be better
efficient (thanks to him) !

To limit the compilation time, we have installed the Ubuntu compiled kernel 
from :
https://kernel.ubuntu.com/mainline/

By bisecting using those versions, here is what we have :

```
v5.15.191 GOOD
v6.0.19   GOOD
v6.1.150  GOOD
v6.2      GOOD
v6.4      GOOD
v6.5.5    GOOD with new error in logs [1]
v6.5.11   GOOD with new error in logs [1]
v6.6.10   GOOD with new error in logs [1]
v6.6.10   GOOD with new error in logs [1]
v6.6.15   GOOD with new error in logs [1]
v6.6.20   BAD  with new error in logs [1]
v6.6.30   BAD  with new error in logs [1]
v6.6.60   BAD  with new error in logs [1]
v6.6.81   BAD  with new error in logs [1]
v6.6.104  BAD  with new error in logs [1]
v6.8.12   BAD  with new error in logs [1]
```

So, we built Linux with gregkh tree :
https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/gregkh.git/refs/tags

We have seen in `git log` output :

9b4a8eac17f0 Linux 6.6.20
51f354b815c4 Linux 6.6.15

We used `git bisect`.

After a lot of time lost by compiling and bisecting (the problem was
always here or never here incoherently) using .config from ubuntu
kernel, vanilla kernel or "localmodconfig", we found that may the
problem is with a .config option and not a kernel code commit.

The `diff config-6.6.15-060615-generic config-6.6.20-060620-generic` is small 
and after some tests, we found where is the problem.
Ubuntu added in 6.6.20 :

```
CONFIG_INTEL_IOMMU_DEFAULT_ON=y
CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON=y
```

And this is what broke the `broadcom-sta-dkms`.

Temporary working solutions :
- Compiling the kernel without those options solves the problem.
- Adding `GRUB_CMDLINE_LINUX_DEFAULT="intel_iommu=off"` to `/etc/default/grub` 
solves the problem.
- Adding `GRUB_CMDLINE_LINUX_DEFAULT="iommu=pt"` to `/etc/default/grub` solves 
the problem.


[1]: The error message :

```
kernel: UBSAN: array-index-out-of-bounds in 
/var/lib/dkms/broadcom-sta/6.30.223.271/build/src/wl/sys/wl_linux.c:1939:4
kernel: index 2 is out of range for type 'ether_addr [1]'
```

-- 
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/2078697

Title:
  Ubuntu 24.04.1 (kernel ?) freeze/crashes when downloading using
  broadcom-sta package

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