[PATCH v5] 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.

Fixes: fb4ee67529ff ("net/ncsi: Add NCSI OEM command support")
Signed-off-by: Kumar Thangavel <redacted>
Acked-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Reviewed-by: Paul Menzel <redacted>

---
  v5:
   - Added Fixes tag
   - Added const variable for padding_bytes

  v4:
   - Used existing macro for max function

  v3:
   - Added Macro for MAX
   - Fixed the missed semicolon

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

  v1:
   - Initial draft

---
---
 net/ncsi/ncsi-cmd.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/net/ncsi/ncsi-cmd.c b/net/ncsi/ncsi-cmd.c
index ba9ae482141b..9571bb4dd991 100644
--- a/net/ncsi/ncsi-cmd.c
+++ b/net/ncsi/ncsi-cmd.c

@@ -18,6 +18,8 @@
 #include "internal.h"
 #include "ncsi-pkt.h"
 
+const unsigned short padding_bytes = 26;
+
 u32 ncsi_calculate_checksum(unsigned char *data, int len)
 {
 	u32 checksum = 0;

@@ -213,12 +215,16 @@ 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)
-		len += 26;
-	else
-		len += nca->payload;
+	len += max(payload, padding_bytes);
 
 	cmd = skb_put_zero(skb, len);
 	memcpy(&cmd->mfr_id, nca->data, nca->payload);

@@ -272,6 +278,7 @@ 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 +288,14 @@ 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)
-		len += 26;
-	else
-		len += nca->payload;
+	payload = ALIGN(nca->payload, 4);
+	len += max(payload, padding_bytes);
 
 	/* Allocate skb */
 	skb = alloc_skb(len, GFP_ATOMIC);

-- 
2.17.1

Hi Kumar,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v5.16-rc1 next-20211115]
[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/20211115-224945
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 8ab774587903771821b59471cc723bba6d893942
config: riscv-randconfig-r026-20211115 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project fbe72e41b99dc7994daac300d208a955be3e4a0a)
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
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        # https://github.com/0day-ci/linux/commit/dc2cde90f4de825ff92f0ad81bc70e132c6ad6ec
        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/20211115-224945
        git checkout dc2cde90f4de825ff92f0ad81bc70e132c6ad6ec
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=riscv 

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

All warnings (new ones prefixed by >>):

quoted

net/ncsi/ncsi-cmd.c:298:9: warning: comparison of distinct pointer types ('typeof (payload) *' (aka 'int *') and 'typeof (padding_bytes) *' (aka 'const unsigned short *')) [-Wcompare-distinct-pointer-types]

           len += max(payload, padding_bytes);
                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/minmax.h:52:19: note: expanded from macro 'max'
   #define max(x, y)       __careful_cmp(x, y, >)
                           ^~~~~~~~~~~~~~~~~~~~~~
   include/linux/minmax.h:36:24: note: expanded from macro '__careful_cmp'
           __builtin_choose_expr(__safe_cmp(x, y), \
                                 ^~~~~~~~~~~~~~~~
   include/linux/minmax.h:26:4: note: expanded from macro '__safe_cmp'
                   (__typecheck(x, y) && __no_side_effects(x, y))
                    ^~~~~~~~~~~~~~~~~
   include/linux/minmax.h:20:28: note: expanded from macro '__typecheck'
           (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
                      ~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~
   1 warning generated.


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

   273	
   274	static struct ncsi_request *ncsi_alloc_command(struct ncsi_cmd_arg *nca)
   275	{
   276		struct ncsi_dev_priv *ndp = nca->ndp;
   277		struct ncsi_dev *nd = &ndp->ndev;
   278		struct net_device *dev = nd->dev;
   279		int hlen = LL_RESERVED_SPACE(dev);
   280		int tlen = dev->needed_tailroom;
   281		int payload;
   282		int len = hlen + tlen;
   283		struct sk_buff *skb;
   284		struct ncsi_request *nr;
   285	
   286		nr = ncsi_alloc_request(ndp, nca->req_flags);
   287		if (!nr)
   288			return NULL;
   289	
   290		/* NCSI command packet has 16-bytes header, payload, 4 bytes checksum.
   291		 * Payload needs padding so that the checksum field following payload is
   292		 * aligned to 32-bit boundary.
   293		 * The packet needs padding if its payload is less than 26 bytes to
   294		 * meet 64 bytes minimal ethernet frame length.
   295		 */
   296		len += sizeof(struct ncsi_cmd_pkt_hdr) + 4;
   297		payload = ALIGN(nca->payload, 4);
 > 298		len += max(payload, padding_bytes);
   299	
   300		/* Allocate skb */
   301		skb = alloc_skb(len, GFP_ATOMIC);
   302		if (!skb) {
   303			ncsi_free_request(nr);
   304			return NULL;
   305		}
   306	
   307		nr->cmd = skb;
   308		skb_reserve(skb, hlen);
   309		skb_reset_network_header(skb);
   310	
   311		skb->dev = dev;
   312		skb->protocol = htons(ETH_P_NCSI);
   313	
   314		return nr;
   315	}
   316	

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

On Mon, 15 Nov 2021 20:18:46 +0530 Kumar Thangavel wrote:

This looks like mixing code and declarations.

If a piece of code is important enough to warrant a comment it should
not be placed as variable init.

payload is int here, and padding_bytes is unsigned short, you either
have to use max_t() or change the types to agree.