Re: [PATCH net-next 12/24] seg6: Use nested-BH locking for seg6_bpf_srh_states.

[kernel test robot]

Hi Sebastian,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Sebastian-Andrzej-Siewior/locking-local_lock-Introduce-guard-definition-for-local_lock/20231216-011911
base:   net-next/main
patch link:    https://lore.kernel.org/r/20231215171020.687342-13-bigeasy%40linutronix.de
patch subject: [PATCH net-next 12/24] seg6: Use nested-BH locking for seg6_bpf_srh_states.
config: x86_64-randconfig-r131-20231216 (https://download.01.org/0day-ci/archive/20231216/202312161151.k1MBvXUD-lkp@xxxxxxxxx/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231216/202312161151.k1MBvXUD-lkp@xxxxxxxxx/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@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202312161151.k1MBvXUD-lkp@xxxxxxxxx/

sparse warnings: (new ones prefixed by >>)
>> net/ipv6/seg6_local.c:1431:9: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected struct local_lock_t [usertype] *l @@     got struct local_lock_t [noderef] __percpu * @@
   net/ipv6/seg6_local.c:1431:9: sparse:     expected struct local_lock_t [usertype] *l
   net/ipv6/seg6_local.c:1431:9: sparse:     got struct local_lock_t [noderef] __percpu *

vim +1431 net/ipv6/seg6_local.c

  1410	
  1411	static int input_action_end_bpf(struct sk_buff *skb,
  1412					struct seg6_local_lwt *slwt)
  1413	{
  1414		struct seg6_bpf_srh_state *srh_state;
  1415		struct ipv6_sr_hdr *srh;
  1416		int ret;
  1417	
  1418		srh = get_and_validate_srh(skb);
  1419		if (!srh) {
  1420			kfree_skb(skb);
  1421			return -EINVAL;
  1422		}
  1423		advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
  1424	
  1425		/* The access to the per-CPU buffer srh_state is protected by running
  1426		 * always in softirq context (with disabled BH). On PREEMPT_RT the
  1427		 * required locking is provided by the following local_lock_nested_bh()
  1428		 * statement. It is also accessed by the bpf_lwt_seg6_* helpers via
  1429		 * bpf_prog_run_save_cb().
  1430		 */
> 1431		scoped_guard(local_lock_nested_bh, &seg6_bpf_srh_states.bh_lock) {
  1432			srh_state = this_cpu_ptr(&seg6_bpf_srh_states);
  1433			srh_state->srh = srh;
  1434			srh_state->hdrlen = srh->hdrlen << 3;
  1435			srh_state->valid = true;
  1436	
  1437			rcu_read_lock();
  1438			bpf_compute_data_pointers(skb);
  1439			ret = bpf_prog_run_save_cb(slwt->bpf.prog, skb);
  1440			rcu_read_unlock();
  1441	
  1442			switch (ret) {
  1443			case BPF_OK:
  1444			case BPF_REDIRECT:
  1445				break;
  1446			case BPF_DROP:
  1447				goto drop;
  1448			default:
  1449				pr_warn_once("bpf-seg6local: Illegal return value %u\n", ret);
  1450				goto drop;
  1451			}
  1452	
  1453			if (srh_state->srh && !seg6_bpf_has_valid_srh(skb))
  1454				goto drop;
  1455		}
  1456	
  1457		if (ret != BPF_REDIRECT)
  1458			seg6_lookup_nexthop(skb, NULL, 0);
  1459	
  1460		return dst_input(skb);
  1461	
  1462	drop:
  1463		kfree_skb(skb);
  1464		return -EINVAL;
  1465	}
  1466	

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