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SubjectRe: [PATCH v2] usb: gadget: ncm: Handle decoding of multiple NTB's in unwrap call
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On 9/17/2023 1:34 PM, Greg Kroah-Hartman wrote:
>> Cc: stable@vger.kernel.org
>
> What commit id does this fix?
>

Hi Greg,

This fixes the initial patch that added the driver:
9f6ce4240a2bf456402c15c06768059e5973f28c

>> Reviewed-by: Maciej Żenczykowski <maze@google.com>
>> Signed-off-by: Krishna Kurapati <quic_kriskura@quicinc.com>
>> ---
>> 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,

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