Re: Null pointer dereference in mcp251x driver when resuming from sleep

[Andy Shevchenko]

On Mon, May 03, 2021 at 04:48:10PM +0300, Andy Shevchenko wrote:
> On Mon, May 03, 2021 at 04:44:24PM +0300, Andy Shevchenko wrote:
> > On Mon, May 03, 2021 at 03:11:40PM +0200, Frieder Schrempf wrote:
> > > Hi,
> > > 
> > > with kernel 5.10.x and 5.12.x I'm getting a null pointer dereference
> > > exception from the mcp251x driver when I resume from sleep (see trace
> > > below).
> > > 
> > > As far as I can tell this was working fine with 5.4. As I currently don't
> > > have the time to do further debugging/bisecting, for now I want to at least
> > > report this here.
> > > 
> > > Maybe there is someone around who could already give a wild guess for what
> > > might cause this just by looking at the trace/code!?
> > 
> > Does revert of c7299fea6769 ("spi: Fix spi device unregister flow") help?
> 
> Other than that, bisecting will take not more than 3-4 iterations only:
> % git log --oneline v5.4..v5.10.34 -- drivers/net/can/spi/mcp251x.c
> 3292c4fc9ce2 can: mcp251x: fix support for half duplex SPI host controllers
> e0e25001d088 can: mcp251x: add support for half duplex controllers
> 74fa565b63dc can: mcp251x: Use readx_poll_timeout() helper
> 2d52dabbef60 can: mcp251x: add GPIO support
> cfc24a0aa7a1 can: mcp251x: sort include files alphabetically
> df561f6688fe treewide: Use fallthrough pseudo-keyword

> 8ce8c0abcba3 can: mcp251x: only reset hardware as required

And only smoking gun by analyzing the code is the above. So, for the first I
would simply check before that commit and immediately after (15-30 minutes of
work). (I would do it myself if I had a hardware at hand...)

> 877a902103fd can: mcp251x: add mcp251x_write_2regs() and make use of it
> 50ec88120ea1 can: mcp251x: get rid of legacy platform data
> 14684b93019a Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

-- 
With Best Regards,
Andy Shevchenko