Re: [PATCH] cxl/mbox: Fix missing variable payload checks in cmd size validation

[Dan Williams <dan.j.williams@intel.com>]

Verma, Vishal L wrote:
> On Tue, 2022-06-28 at 14:42 -0700, Alison Schofield wrote:
> > On Tue, Jun 28, 2022 at 01:04:27PM -0700, Vishal Verma wrote:
> > > The conversion of command sizes to unsigned missed a couple of
> > > checks
> > > against variable size payloads during command validation, which
> > > made all
> > > variable payload commands unconditionally fail. Add the checks back
> > > using
> > > the new CXL_VARIABLE_PAYLOAD scheme.
> > > 
> > > Reported-by: Abhi Cs <abhi.cs@intel.com>
> > > Fixes: 26f89535a5bb ("cxl/mbox: Use type __u32 for mailbox payload
> > > sizes")
> > > Cc: <stable@vger.kernel.org>
> > > Cc: Ira Weiny <ira.weiny@intel.com>
> > > Cc: Dan Williams <dan.j.williams@intel.com>
> > > Cc: Alison Schofield <alison.schofield@intel.com>
> > > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> > 
> > with one caveat below...
> > Reviewed-by: Alison Schofield <alison.schofield@intel.com>
> 
> Thanks for the review!
> 
> 
> > > ---
> > >  drivers/cxl/core/mbox.c | 10 ++++++----
> > >  1 file changed, 6 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> > > index 40e3ccb2bf3e..d929b89d12a7 100644
> > > --- a/drivers/cxl/core/mbox.c
> > > +++ b/drivers/cxl/core/mbox.c
> > > @@ -355,12 +355,14 @@ static int cxl_to_mem_cmd(struct
> > > cxl_mem_command *mem_cmd,
> > >                 return -EBUSY;
> > >  
> > >         /* Check the input buffer is the expected size */
> > > -       if (info->size_in != send_cmd->in.size)
> > > -               return -ENOMEM;
> > > +       if (info->size_in != CXL_VARIABLE_PAYLOAD)
> > > +               if (info->size_in != send_cmd->in.size)
> > > +                       return -ENOMEM;
> > 
> > We can leave it to Dan to arbitrate, but I don't think nested
> > if's without brackets follow kernel coding style.
> > 
> > However, Dan didn't like my nested if's with brackets either.
> > He'd prefer using &&
> 
> Ha funny - I had && originally, but then I spotted nested if () a few
> lines above in the same file in cxl_mbox_send_cmd(), and switched to
> the same style :)
> 
> I'd be happy to change to &&.

Yeah, lets go that route.

/me thanks Alison for catching it.