usb: cdc-acm: BUG kmalloc-128 Poison overwritten

Bruno Thomsen bruno.thomsen at
Wed Feb 24 10:21:08 EST 2021

Den man. 22. feb. 2021 kl. 10.36 skrev Oliver Neukum <oneukum at>:
> Am Donnerstag, den 18.02.2021, 16:52 +0100 schrieb Bruno Thomsen:
> > Den fre. 12. feb. 2021 kl. 16.33 skrev Bruno Thomsen <bruno.thomsen at>:
> > > Hi,
> > >
> > > I have been experience random kernel oops in the cdc-acm driver on
> > > imx7 (arm arch). Normally it happens during the first 1-3min runtime
> > > after power-on. Below oops is from 5.8.17 mainline kernel with an
> > > extra patch back-ported in an attempt to fix it:
> > > 38203b8385 ("usb: cdc-acm: fix cooldown mechanism")
> >
> > I can now boot board with 5.11 kernel without any extra patches and
> > it produce similar issue. Hopefully that make the oops more useful.
> > Issue has been seen on multiple devices, so I don't think it's a bad
> > hardware issue.
> is this a regression from 5.10?

Hi Oliver

No, this is not a regression from 5.10. It seems that many attempts to
fix cdc-acm in the 5.x kernel series have failed to fix the root cause of
these oops. I have not seen this on 4.14 and 4.19, but I have observed
it on at least 5.3 and newer kernels in slight variations.
I guess this is because cdc-acm is very common in the embedded
ARM world and rarely used on servers or laptops. Combined with
ARM devices still commonly use 4.x LTS kernels. Not sure if
hardening options on the kernel has increased change of reproducing

I am ready to test new patches and will continue to report oops


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