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

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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,




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