linux-kernel - Re: [PATCH bpf-next v4 1/4] bpf: Generalize bpf_sk

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Date:   Mon, 20 Jul 2020 19:18:14 +0800
From:   kernel test robot <lkp@...el.com>
To:     KP Singh <kpsingh@...omium.org>, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, linux-security-module@...r.kernel.org
Cc:     kbuild-all@...ts.01.org, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Paul Turner <pjt@...gle.com>, Jann Horn <jannh@...gle.com>,
        Florent Revest <revest@...omium.org>
Subject: Re: [PATCH bpf-next v4 1/4] bpf: Generalize bpf_sk_storage

Hi KP,

I love your patch! Perhaps something to improve:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/0day-ci/linux/commits/KP-Singh/Generalizing-bpf_local_storage/20200709-181906
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: s390-randconfig-s032-20200719 (attached as .config)
compiler: s390-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.2-49-g707c5017-dirty
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=s390 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>


sparse warnings: (new ones prefixed by >>)

>> kernel/bpf/bpf_local_storage.c:237:16: sparse: sparse: non size-preserving integer to pointer cast

vim +237 kernel/bpf/bpf_local_storage.c

   221	
   222	/* Publish local_storage to the address.  This is used because we are already
   223	 * in a region where we cannot grab a lock on the object owning the storage (
   224	 * (e.g sk->sk_lock). Hence, atomic ops is used.
   225	 *
   226	 * From now on, the addr pointer is protected
   227	 * by the local_storage->lock.  Hence, upon freeing,
   228	 * the local_storage->lock must be held before unlinking the storage from the
   229	 * owner.
   230	 */
   231	int bpf_local_storage_publish(struct bpf_local_storage_elem *first_selem,
   232				      struct bpf_local_storage **addr,
   233				      struct bpf_local_storage *curr)
   234	{
   235		struct bpf_local_storage *prev;
   236	
 > 237		prev = cmpxchg(addr, NULL, curr);
   238		if (unlikely(prev)) {
   239			/* Note that even first_selem was linked to smap's
   240			 * bucket->list, first_selem can be freed immediately
   241			 * (instead of kfree_rcu) because
   242			 * bpf_local_storage_map_free() does a
   243			 * synchronize_rcu() before walking the bucket->list.
   244			 * Hence, no one is accessing selem from the
   245			 * bucket->list under rcu_read_lock().
   246			 */
   247			bpf_selem_unlink_map(first_selem);
   248			return -EAGAIN;
   249		}
   250	
   251		return 0;
   252	}
   253	

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

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