Re: [PATCH v2 1/5] mfd: cgbc: Fix use of negative error code as valid session handle

[Lee Jones]

On Wed, 02 Sep 2026, Lee Jones wrote:

> On Tue, 11 Aug 2026, Thomas Richard (congatec GmbH) wrote:
> 
> > The cgbc_session_command() return value was directly cast to u8 and used
> > as session handle without error checking. Casting a negative error to u8
> > produces a valid-looking session handle. So check if return value is
> > positive before to cast and use it.
> > 
> > Cc: stable@xxxxxxxxxxxxxxx
> > Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
> > Closes: https://sashiko.dev/#/patchset/20260713-cgbc-core-fix-cgbc-remove-v1-1-79274ad62b3a%40bootlin.com?part=1
> > Fixes: 6f1067cfbee7 ("mfd: Add Congatec Board Controller driver")
> > Signed-off-by: Thomas Richard (congatec GmbH) <thomas.richard@xxxxxxxxxxx>
> > ---
> >  drivers/mfd/cgbc-core.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mfd/cgbc-core.c b/drivers/mfd/cgbc-core.c
> > index 2becaf797646..4a409234e66c 100644
> > --- a/drivers/mfd/cgbc-core.c
> > +++ b/drivers/mfd/cgbc-core.c
> > @@ -103,7 +103,11 @@ static int cgbc_session_request(struct cgbc_device_data *cgbc)
> >  	if (ret)
> >  		return dev_err_probe(cgbc->dev, ret, "device not found or not ready\n");
> >  
> > -	cgbc->session = cgbc_session_command(cgbc, CGBC_SESSION_CMD_REQUEST);
> > +	ret = cgbc_session_command(cgbc, CGBC_SESSION_CMD_REQUEST);
> > +	if (ret < 0)
> > +		return dev_err_probe(cgbc->dev, ret, "session handle request timed out\n");
> 
> Can we make this a bit more user friendly?
> 
> "Failed to start XYZ session"?

The other two MFD patches are fine.

-- 
Lee Jones