Re: [PATCH net v2 1/1] net: gso: limit recursive IP-in-IP segmentation

[kernel test robot <lkp@intel.com>]

:::::: 
:::::: Manual check reason: "low confidence static check warning: include/net/gso.h:35:13: sparse: sparse: unsigned value that used to be signed checked against zero?"
:::::: 

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <33280f6e07bccaaeef2c70f1754017e9517f5aa5.1789618203.git.zihanx@nebusec.ai>
References: <33280f6e07bccaaeef2c70f1754017e9517f5aa5.1789618203.git.zihanx@nebusec.ai>
TO: Zihan Xi <zihanx@nebusec.ai>
TO: netdev@vger.kernel.org
CC: zihanx@nebusec.ai
CC: davem@davemloft.net
CC: edumazet@google.com
CC: kuba@kernel.org
CC: pabeni@redhat.com
CC: horms@kernel.org
CC: steffen.klassert@secunet.com
CC: herbert@gondor.apana.org.au
CC: dsahern@kernel.org
CC: idosch@nvidia.com
CC: linux-kernel@vger.kernel.org
CC: stable@vger.kernel.org

Hi Zihan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net/main]
[also build test WARNING on klassert-ipsec-next/master klassert-ipsec/master net-next/main linus/master v7.3-rc3 next-20260916]
[cannot apply to linux-review/Zihan-Xi/net-gso-limit-recursive-IP-in-IP-segmentation/20260913-141212]
[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#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Zihan-Xi/net-gso-limit-recursive-IP-in-IP-segmentation/20260917-160041
base:   net/main
patch link:    https://lore.kernel.org/r/33280f6e07bccaaeef2c70f1754017e9517f5aa5.1789618203.git.zihanx%40nebusec.ai
patch subject: [PATCH net v2 1/1] net: gso: limit recursive IP-in-IP segmentation
:::::: branch date: 18 hours ago
:::::: commit date: 18 hours ago
config: sh-randconfig-r1307-20260918 (https://download.01.org/0day-ci/archive/20260918/202609181814.iLdC7fhe-lkp@intel.com/config)
compiler: sh4-linux-gcc (GCC) 16.1.0
sparse: v0.6.5-rc1
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260918/202609181814.iLdC7fhe-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/r/202609181814.iLdC7fhe-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   net/ipv6/ip6_offload.c: note: in included file (through include/net/udp.h):
>> include/net/gso.h:35:13: sparse: sparse: unsigned value that used to be signed checked against zero?
   include/net/gso.h:35:13: sparse: signed value source
>> include/net/gso.h:35:13: sparse: sparse: unsigned value that used to be signed checked against zero?
   include/net/gso.h:35:13: sparse: signed value source

vim +35 include/net/gso.h

16f1d23d914a29 Zihan Xi 2026-09-17  29  
16f1d23d914a29 Zihan Xi 2026-09-17  30  static inline bool gso_header_len_add(struct sk_buff *skb,
16f1d23d914a29 Zihan Xi 2026-09-17  31  				      unsigned int len)
16f1d23d914a29 Zihan Xi 2026-09-17  32  {
16f1d23d914a29 Zihan Xi 2026-09-17  33  	struct skb_gso_cb *cb = SKB_GSO_CB(skb);
16f1d23d914a29 Zihan Xi 2026-09-17  34  
16f1d23d914a29 Zihan Xi 2026-09-17 @35  	if (unlikely(cb->gso_header_len > GSO_MAX_HEADER ||
16f1d23d914a29 Zihan Xi 2026-09-17  36  		     len > GSO_MAX_HEADER - cb->gso_header_len))
16f1d23d914a29 Zihan Xi 2026-09-17  37  		return true;
16f1d23d914a29 Zihan Xi 2026-09-17  38  
16f1d23d914a29 Zihan Xi 2026-09-17  39  	cb->gso_header_len += len;
16f1d23d914a29 Zihan Xi 2026-09-17  40  	return false;
16f1d23d914a29 Zihan Xi 2026-09-17  41  }
16f1d23d914a29 Zihan Xi 2026-09-17  42  

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