On 5/25/2021 8:43 AM, Greg Kroah-Hartman wrote:

On Tue, May 25, 2021 at 08:38:34AM +0200, Arend van Spriel wrote:

quoted

On 5/24/2021 4:48 PM, Sasha Levin wrote:

quoted

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

[ Upstream commit 419b4a142a7ece36cebcd434f8ce2af59ef94b85 ]

The brcmfmac driver ignores any errors on initialization with the
different busses by deferring the initialization to a workqueue and
ignoring all possible errors that might happen.  Fix up all of this by
only allowing the module to load if all bus registering worked properly.

Hi Greg,

Saw this one flying by for stable kernel. Actually the first time I saw this
patch, because I don't follow LKML as much as linux-wireless. The patch is
fine, but wanted to give some context on the workqueue approach. It was
there for historic reasons. Back then we had the UMH to provide firmware
loading and because we request firmware during driver probe we could cause
kernel boot to show significant delay when driver was built-in. Hence the
workqueue which allowed kernel boot to proceed and driver probe was running
in another thread context. These days we have direct firmware loading from
the kernel and brcmfmac uses the asynchronous firmware loading API so there
is indeed no longer a need for the workqueue.

Just for my understanding could you explain the motivation behind this
change. In the preceding revert patch I saw this remark:

"""
The original commit here did nothing to actually help if usb_register()
failed, so it gives a "false sense of security" when there is none.  The
correct solution is to correctly unwind from this error.
"""

Does this mean the patch is addressing some security issue. Before your
patch the module would remain loaded despite a bus register failure. I guess
there is a story behind this that I am curious about.

The module would remain loaded, yes, but nothing would work, and so no
one would have any idea that something went wrong.  The original commit
was wrong, it did not actually solve anything.

Agree.

This commit properly propagates any error that happens back to the user,
like any other module being loaded.

I understand, but this might cause a regression for the user. For 
instance if the usb_register() fails, but the other driver registrations 
succeed and the user has a wireless PCIe device. Before this change the 
user would have a functioning wifi device, but with this change it does not?

Regards,
Arend

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