[PATCH v2] Add payload to be 32-bit aligned to fix dropped packets

Update NC-SI command handler (both standard and OEM) to take into
account of payload paddings in allocating skb (in case of payload
size is not 32-bit aligned).

The checksum field follows payload field, without taking payload
padding into account can cause checksum being truncated, leading to
dropped packets.

Signed-off-by: Kumar Thangavel <redacted>
Acked-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Reviewed-by: Paul Menzel <redacted>

---
  v2:
   - Added NC-SI spec version and section
   - Removed blank line
   - corrected spellings

  v1:
   - Initial draft.

---
 net/ncsi/ncsi-cmd.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/net/ncsi/ncsi-cmd.c b/net/ncsi/ncsi-cmd.c
index ba9ae482141b..29a75b79a811 100644
--- a/net/ncsi/ncsi-cmd.c
+++ b/net/ncsi/ncsi-cmd.c

@@ -213,12 +213,19 @@ static int ncsi_cmd_handler_oem(struct sk_buff *skb,
 {
 	struct ncsi_cmd_oem_pkt *cmd;
 	unsigned int len;
+	/* NC-SI spec DSP_0222_1.2.0, section 8.2.2.2
+	 * requires payload to be padded with 0 to
+	 * 32-bit boundary before the checksum field.
+	 * Ensure the padding bytes are accounted for in
+	 * skb allocation
+	 */
+	unsigned short payload = ALIGN(nca->payload, 4);
 
 	len = sizeof(struct ncsi_cmd_pkt_hdr) + 4;
-	if (nca->payload < 26)
+	if (payload < 26)
 		len += 26;
 	else
-		len += nca->payload;
+		len += payload;
 
 	cmd = skb_put_zero(skb, len);
 	memcpy(&cmd->mfr_id, nca->data, nca->payload);

@@ -272,6 +279,7 @@ static struct ncsi_request *ncsi_alloc_command(struct ncsi_cmd_arg *nca)
 	struct net_device *dev = nd->dev;
 	int hlen = LL_RESERVED_SPACE(dev);
 	int tlen = dev->needed_tailroom;
+	int payload;
 	int len = hlen + tlen;
 	struct sk_buff *skb;
 	struct ncsi_request *nr;

@@ -281,14 +289,17 @@ static struct ncsi_request *ncsi_alloc_command(struct ncsi_cmd_arg *nca)
 		return NULL;
 
 	/* NCSI command packet has 16-bytes header, payload, 4 bytes checksum.
+	 * Payload needs padding so that the checksum field following payload is
+	 * aligned to 32-bit boundary.
 	 * The packet needs padding if its payload is less than 26 bytes to
 	 * meet 64 bytes minimal ethernet frame length.
 	 */
 	len += sizeof(struct ncsi_cmd_pkt_hdr) + 4;
-	if (nca->payload < 26)
+	payload = ALIGN(nca->payload, 4)
+	if (payload < 26)
 		len += 26;
 	else
-		len += nca->payload;
+		len += payload;
 
 	/* Allocate skb */
 	skb = alloc_skb(len, GFP_ATOMIC);

-- 
2.17.1

On Tue, 19 Oct 2021 20:11:27 +0530 Kumar Thangavel wrote:

 	len += sizeof(struct ncsi_cmd_pkt_hdr) + 4;
-	if (nca->payload < 26)
+	payload = ALIGN(nca->payload, 4)
+	if (payload < 26)
 		len += 26;
 	else
-		len += nca->payload;
+		len += payload;

You round up to 4 and then add 26 if the result is smaller.  26 is not
a multiple of 4. Is this intentional?

Also you can write this on one line:

	len += max(payload, 26);

On Tue, 19 Oct 2021 20:11:27 +0530 Kumar Thangavel wrote:

+	payload = ALIGN(nca->payload, 4)

This is missing a semicolon.

Hi Kumar,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.15-rc6 next-20211019]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Kumar-Thangavel/Add-payload-to-be-32-bit-aligned-to-fix-dropped-packets/20211019-225018
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 519d81956ee277b4419c723adfb154603c2565ba
config: i386-randconfig-a005-20211019 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project b37efed957ed0a0193d80020aefd55cb587dfc1f)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/177d89a1966a0830ac30b8962ac9af76c1d675ae
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Kumar-Thangavel/Add-payload-to-be-32-bit-aligned-to-fix-dropped-packets/20211019-225018
        git checkout 177d89a1966a0830ac30b8962ac9af76c1d675ae
        # save the attached .config to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash net/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

All errors (new ones prefixed by >>):

quoted

net/ncsi/ncsi-cmd.c:298:34: error: expected ';' after expression

           payload = ALIGN(nca->payload, 4)
                                           ^
                                           ;
   1 error generated.


vim +298 net/ncsi/ncsi-cmd.c

   274	
   275	static struct ncsi_request *ncsi_alloc_command(struct ncsi_cmd_arg *nca)
   276	{
   277		struct ncsi_dev_priv *ndp = nca->ndp;
   278		struct ncsi_dev *nd = &ndp->ndev;
   279		struct net_device *dev = nd->dev;
   280		int hlen = LL_RESERVED_SPACE(dev);
   281		int tlen = dev->needed_tailroom;
   282		int payload;
   283		int len = hlen + tlen;
   284		struct sk_buff *skb;
   285		struct ncsi_request *nr;
   286	
   287		nr = ncsi_alloc_request(ndp, nca->req_flags);
   288		if (!nr)
   289			return NULL;
   290	
   291		/* NCSI command packet has 16-bytes header, payload, 4 bytes checksum.
   292		 * Payload needs padding so that the checksum field following payload is
   293		 * aligned to 32-bit boundary.
   294		 * The packet needs padding if its payload is less than 26 bytes to
   295		 * meet 64 bytes minimal ethernet frame length.
   296		 */
   297		len += sizeof(struct ncsi_cmd_pkt_hdr) + 4;
 > 298		payload = ALIGN(nca->payload, 4)
   299		if (payload < 26)
   300			len += 26;
   301		else
   302			len += payload;
   303	
   304		/* Allocate skb */
   305		skb = alloc_skb(len, GFP_ATOMIC);
   306		if (!skb) {
   307			ncsi_free_request(nr);
   308			return NULL;
   309		}
   310	
   311		nr->cmd = skb;
   312		skb_reserve(skb, hlen);
   313		skb_reset_network_header(skb);
   314	
   315		skb->dev = dev;
   316		skb->protocol = htons(ETH_P_NCSI);
   317	
   318		return nr;
   319	}
   320	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org