Re: [PATCH net v3 2/2] xsk: Fix zero-copy AF_XDP fragment drop

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

Hi Nikhil,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Nikhil-P-Rao/xsk-Fix-fragment-node-deletion-to-prevent-buffer-leak/20260217-092448
base:   net/main
patch link:    https://lore.kernel.org/r/20260217012346.22468-3-nikhil.rao%40amd.com
patch subject: [PATCH net v3 2/2] xsk: Fix zero-copy AF_XDP fragment drop
config: powerpc64-randconfig-002-20260217 (https://download.01.org/0day-ci/archive/20260217/202602172046.vf9DtpdF-lkp@intel.com/config)
compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project e86750b29fa0ff207cd43213d66dabe565417638)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260217/202602172046.vf9DtpdF-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/oe-kbuild-all/202602172046.vf9DtpdF-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> net/xdp/xsk.c:183:6: warning: variable 'err' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
     183 |         if (xskq_prod_nb_free(xs->rx, num_desc) < num_desc) {
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   net/xdp/xsk.c:201:9: note: uninitialized use occurs here
     201 |         return err;
         |                ^~~
   net/xdp/xsk.c:183:2: note: remove the 'if' if its condition is always false
     183 |         if (xskq_prod_nb_free(xs->rx, num_desc) < num_desc) {
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     184 |                 xs->rx_queue_full++;
         |                 ~~~~~~~~~~~~~~~~~~~~
     185 |                 goto err;
         |                 ~~~~~~~~~
     186 |         }
         |         ~
   net/xdp/xsk.c:171:9: note: initialize the variable 'err' to silence this warning
     171 |         int err;
         |                ^
         |                 = 0
   1 warning generated.


vim +183 net/xdp/xsk.c

   162	
   163	static int xsk_rcv_zc(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
   164	{
   165		struct xdp_buff_xsk *xskb = container_of(xdp, struct xdp_buff_xsk, xdp);
   166		u32 frags = xdp_buff_has_frags(xdp);
   167		struct xdp_buff_xsk *pos, *tmp;
   168		struct list_head *xskb_list;
   169		u32 contd = 0;
   170		u32 num_desc;
   171		int err;
   172	
   173		if (frags) {
   174			num_desc = xdp_get_shared_info_from_buff(xdp)->nr_frags + 1;
   175			contd = XDP_PKT_CONTD;
   176		} else {
   177			err = __xsk_rcv_zc(xs, xskb, len, contd);
   178			if (err)
   179				goto err;
   180			return 0;
   181		}
   182	
 > 183		if (xskq_prod_nb_free(xs->rx, num_desc) < num_desc) {
   184			xs->rx_queue_full++;
   185			goto err;
   186		}
   187	
   188		__xsk_rcv_zc(xs, xskb, len, contd);
   189		xskb_list = &xskb->pool->xskb_list;
   190		list_for_each_entry_safe(pos, tmp, xskb_list, list_node) {
   191			if (list_is_singular(xskb_list))
   192				contd = 0;
   193			len = pos->xdp.data_end - pos->xdp.data;
   194			__xsk_rcv_zc(xs, pos, len, contd);
   195			list_del_init(&pos->list_node);
   196		}
   197	
   198		return 0;
   199	err:
   200		xsk_buff_free(xdp);
   201		return err;
   202	}
   203	

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