Re: [PATCH v2] usb: gadget: ncm: Handle decoding of multiple NTB's in unwrap call

[Krishna Kurapati PSSNV]

On 9/18/2023 1:07 PM, Krishna Kurapati PSSNV wrote:
> On 9/17/2023 1:34 PM, Greg Kroah-Hartman wrote:
> > > Cc: stable@xxxxxxxxxxxxxxx
> >
> > What commit id does this fix?
>
> Hi Greg,
>
> This fixes the initial patch that added the driver:
> 9f6ce4240a2bf456402c15c06768059e5973f28c
>
> > > Reviewed-by: Maciej Żenczykowski <maze@xxxxxxxxxx>
> > > Signed-off-by: Krishna Kurapati <quic_kriskura@xxxxxxxxxxx>
> > > ---
> > >   drivers/usb/gadget/function/f_ncm.c | 26 +++++++++++++++++++-------
> > >   1 file changed, 19 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/usb/gadget/function/f_ncm.c 
> > > b/drivers/usb/gadget/function/f_ncm.c
> > > index feccf4c8cc4f..f00f051438ec 100644
> > > --- a/drivers/usb/gadget/function/f_ncm.c
> > > +++ b/drivers/usb/gadget/function/f_ncm.c
> > > @@ -1156,7 +1156,8 @@ static int ncm_unwrap_ntb(struct gether *port,
> > >                 struct sk_buff_head *list)
> > >   {
> > >       struct f_ncm    *ncm = func_to_ncm(&port->func);
> > > -    __le16        *tmp = (void *) skb->data;
> > > +    unsigned char    *ntb_ptr = (void *) skb->data;
> >
> > Why persist with the extra ' ', didn't checkpatch complain about this?
> >
> > And why the cast at all?
> My bad. I ran the checkpatch and got the following result:
>
> kriskura@hu-kriskura-hyd:/local/mnt/workspace/krishna/510/testncm/kernel$ ./scripts/checkpatch.pl --strict 0001-usb-gadget-ncm-Handle-decoding-of-multiple-NTB-s-in-.patch
> WARNING: Prefer a maximum 75 chars per line (possible unwrapped commit 
> description?)
> #12:
> unwraps the obtained request data assuming only one NTB is present, we 
> loose
>
> CHECK: No space is necessary after a cast
> #34: FILE: drivers/usb/gadget/function/f_ncm.c:1159:
> +       unsigned char   *ntb_ptr = (void *) skb->data;
>
> CHECK: No space is necessary after a cast
> #46: FILE: drivers/usb/gadget/function/f_ncm.c:1176:
> +       tmp = (void *) ntb_ptr;
>
> CHECK: No space is necessary after a cast
> #93: FILE: drivers/usb/gadget/function/f_ncm.c:1329:
> +               ntb_ptr = (unsigned char *) (ntb_ptr + block_len);
>
> total: 0 errors, 1 warnings, 3 checks, 67 lines checked
>
>
> I ignored the checks and saw only that errors are 0. Seems like I missed 
> fixing the commit text wrapping to 75 chars (On line 12 it has 76 
> chars). Will fix it up in v3.
>
> As per the cast, I initially didn't add any cast and saw that the code 
> was not able to parse the dwSignature of the NTH and decoding of all 
> packets was failing. Only when I added the cast, was the function able 
> to decode all packets properly.
>
> > > +    __le16        *tmp;
> > >       unsigned    index, index2;
> > >       int        ndp_index;
> > >       unsigned    dg_len, dg_len2;
> > > @@ -1169,6 +1170,10 @@ static int ncm_unwrap_ntb(struct gether *port,
> > >       const struct ndp_parser_opts *opts = ncm->parser_opts;
> > >       unsigned    crc_len = ncm->is_crc ? sizeof(uint32_t) : 0;
> > >       int        dgram_counter;
> > > +    int        to_process = skb->len;
> > > +
> > > +parse_ntb:
> > > +    tmp = (void *) ntb_ptr;
> >
> > Again, no blank space please.
> >
> > And why the cast?
> the second cast here was just to be in sync with the original code;
> __le16        *tmp = (void *) skb->data;
>
> I didn't try removing this and running the test. Will check if the 
> second one is required or if decoding is proper without it or not.
>
> Regards,
> Krishna,

Hi Greg,

 I rechecked the code and I don't see any error if I remove the 
typecast for ntb_ptr. If I remove the typecast for tmp, I see build 
errors as ntb_ptr is unsigned char and tmp is __le16. I have pushed v3 
removing the typecast for ntb_ptr and fixing the checkpatch errors. 
Thanks for pointing out that the typecast is not needed.

Regards,
Krishna,