[BUG]: Kernel 4.9: Kernel crash at fs/sysfs/file.c : sysfs_kf_seq_show

[Greg Kroah-Hartman]

On Wed, Jan 13, 2021 at 01:26:11PM +0100, Greg Kroah-Hartman wrote:
> On Wed, Jan 13, 2021 at 05:35:18PM +0530, Pintu Agarwal wrote:
> > On Tue, 12 Jan 2021 at 17:39, Greg Kroah-Hartman
> > <gregkh at linuxfoundation.org> wrote:
> > >
> > > On Tue, Jan 12, 2021 at 05:31:54PM +0530, Pintu Agarwal wrote:
> > > > Hi,
> > > >
> > > > I am using Kernel: 4.9.217 for one of the ARM32 boards for Qualcomm SOC.
> > > > https://github.com/android-linux-stable/msm-4.9
> > > >
> > > > But I think this is a general bug applicable to :Kernel 4.9 under
> > > > fs/sysfs/file.c
> > > > So, I wanted to quickly check here if others are familiar with this
> > > > issue and if it is fixed already.
> > > > Note, this issue does not occur in 4.14 Kernel.
> > > >
> > > > When I execute below command, the Kernel is crashing.
> > > > I tried to add few debug prints to find more details. I see that the
> > > > ops->show pointer is not valid (seems corrupted).
> > > > So I wanted to understand how this can happen only for this particular node.
> > > > Other sysfs entries are working fine.
> > > >
> > 
> > I see that this issue was reported earlier as well by others.
> > https://syzkaller.appspot.com/bug?id=2ec2a9da5c711df3d3d12071bac487b96e75e103
> > https://gitlab.freedesktop.org/drm/amd/-/issues/413
> > https://bugzilla.redhat.com/show_bug.cgi?id=1615070
> > 
> > So it seems to be common issue and thus I wanted to check here if its similar.
> 
> It's "common" in that this is core kernel code that any number of
> drivers could be causing to work incorrectly.  Try fixing up the driver
> code, and odds are, that will fix this issue.
> 
> good luck, and again, go ask for support from your vendor, you are
> paying for that!

And, if you look close at the above links, you will see where the error
is, and what the out-of-tree code needs to to do be fixed up properly.
An exercise for that is left for the vendor :)

greg k-h