[linux-next:master 3337/11397] drivers/net/ethernet/pensando/ionic/ionic_txrx.c:149 ionic_rx_frags() warn: variable dereferenced before check 'buf_info->page' (see line 137)

[linux-next:master 3337/11397] drivers/net/ethernet/pensando/ionic/ionic_txrx.c:149 ionic_rx_frags() warn: variable dereferenced before check 'buf_info->page' (see line 137)

[kernel test robot]

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CC: kbuild-all(a)lists.01.org
CC: Linux Memory Management List <linux-mm@kvack.org>
TO: Shannon Nelson <snelson@pensando.io>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   52c7b727581fe725f8b8a283af21fe0651c73c48
commit: e75ccac1d0644c9d7ad531cb9a81c499930c06da [3337/11397] ionic: use fewer inits on the buf_info struct
:::::: branch date: 12 hours ago
:::::: commit date: 5 weeks ago
config: x86_64-randconfig-m031-20210831 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

smatch warnings:
drivers/net/ethernet/pensando/ionic/ionic_txrx.c:149 ionic_rx_frags() warn: variable dereferenced before check 'buf_info->page' (see line 137)

vim +149 drivers/net/ethernet/pensando/ionic/ionic_txrx.c

2b5720f26908571 Shannon Nelson 2021-03-10  118  
08f2e4b2b2008ce Shannon Nelson 2019-10-23  119  static struct sk_buff *ionic_rx_frags(struct ionic_queue *q,
08f2e4b2b2008ce Shannon Nelson 2019-10-23  120  				      struct ionic_desc_info *desc_info,
a25edab93b2877f Shannon Nelson 2021-03-10  121  				      struct ionic_rxq_comp *comp)
0f3154e6bcb3549 Shannon Nelson 2019-09-03  122  {
89e572e7369fd9a Shannon Nelson 2021-03-10  123  	struct net_device *netdev = q->lif->netdev;
4b0a7539a3728f0 Shannon Nelson 2021-03-10  124  	struct ionic_buf_info *buf_info;
89e572e7369fd9a Shannon Nelson 2021-03-10  125  	struct ionic_rx_stats *stats;
f37bc3462e80d2d Shannon Nelson 2021-03-10  126  	struct device *dev = q->dev;
08f2e4b2b2008ce Shannon Nelson 2019-10-23  127  	struct sk_buff *skb;
08f2e4b2b2008ce Shannon Nelson 2019-10-23  128  	unsigned int i;
08f2e4b2b2008ce Shannon Nelson 2019-10-23  129  	u16 frag_len;
08f2e4b2b2008ce Shannon Nelson 2019-10-23  130  	u16 len;
08f2e4b2b2008ce Shannon Nelson 2019-10-23  131  
89e572e7369fd9a Shannon Nelson 2021-03-10  132  	stats = q_to_rx_stats(q);
89e572e7369fd9a Shannon Nelson 2021-03-10  133  
4b0a7539a3728f0 Shannon Nelson 2021-03-10  134  	buf_info = &desc_info->bufs[0];
08f2e4b2b2008ce Shannon Nelson 2019-10-23  135  	len = le16_to_cpu(comp->len);
08f2e4b2b2008ce Shannon Nelson 2019-10-23  136  
e75ccac1d0644c9 Shannon Nelson 2021-07-27 @137  	prefetchw(buf_info->page);
08f2e4b2b2008ce Shannon Nelson 2019-10-23  138  
89e572e7369fd9a Shannon Nelson 2021-03-10  139  	skb = napi_get_frags(&q_to_qcq(q)->napi);
89e572e7369fd9a Shannon Nelson 2021-03-10  140  	if (unlikely(!skb)) {
89e572e7369fd9a Shannon Nelson 2021-03-10  141  		net_warn_ratelimited("%s: SKB alloc failed on %s!\n",
89e572e7369fd9a Shannon Nelson 2021-03-10  142  				     netdev->name, q->name);
89e572e7369fd9a Shannon Nelson 2021-03-10  143  		stats->alloc_err++;
08f2e4b2b2008ce Shannon Nelson 2019-10-23  144  		return NULL;
89e572e7369fd9a Shannon Nelson 2021-03-10  145  	}
08f2e4b2b2008ce Shannon Nelson 2019-10-23  146  
08f2e4b2b2008ce Shannon Nelson 2019-10-23  147  	i = comp->num_sg_elems + 1;
08f2e4b2b2008ce Shannon Nelson 2019-10-23  148  	do {
4b0a7539a3728f0 Shannon Nelson 2021-03-10 @149  		if (unlikely(!buf_info->page)) {
08f2e4b2b2008ce Shannon Nelson 2019-10-23  150  			dev_kfree_skb(skb);
08f2e4b2b2008ce Shannon Nelson 2019-10-23  151  			return NULL;
0f3154e6bcb3549 Shannon Nelson 2019-09-03  152  		}
0f3154e6bcb3549 Shannon Nelson 2019-09-03  153  
4b0a7539a3728f0 Shannon Nelson 2021-03-10  154  		frag_len = min_t(u16, len, IONIC_PAGE_SIZE - buf_info->page_offset);
08f2e4b2b2008ce Shannon Nelson 2019-10-23  155  		len -= frag_len;
08f2e4b2b2008ce Shannon Nelson 2019-10-23  156  
4b0a7539a3728f0 Shannon Nelson 2021-03-10  157  		dma_sync_single_for_cpu(dev,
4b0a7539a3728f0 Shannon Nelson 2021-03-10  158  					buf_info->dma_addr + buf_info->page_offset,
4b0a7539a3728f0 Shannon Nelson 2021-03-10  159  					frag_len, DMA_FROM_DEVICE);
4b0a7539a3728f0 Shannon Nelson 2021-03-10  160  
08f2e4b2b2008ce Shannon Nelson 2019-10-23  161  		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
4b0a7539a3728f0 Shannon Nelson 2021-03-10  162  				buf_info->page, buf_info->page_offset, frag_len,
4b0a7539a3728f0 Shannon Nelson 2021-03-10  163  				IONIC_PAGE_SIZE);
4b0a7539a3728f0 Shannon Nelson 2021-03-10  164  
4b0a7539a3728f0 Shannon Nelson 2021-03-10  165  		if (!ionic_rx_buf_recycle(q, buf_info, frag_len)) {
4b0a7539a3728f0 Shannon Nelson 2021-03-10  166  			dma_unmap_page(dev, buf_info->dma_addr,
4b0a7539a3728f0 Shannon Nelson 2021-03-10  167  				       IONIC_PAGE_SIZE, DMA_FROM_DEVICE);
e75ccac1d0644c9 Shannon Nelson 2021-07-27  168  			buf_info->page = NULL;
4b0a7539a3728f0 Shannon Nelson 2021-03-10  169  		}
4b0a7539a3728f0 Shannon Nelson 2021-03-10  170  
4b0a7539a3728f0 Shannon Nelson 2021-03-10  171  		buf_info++;
4b0a7539a3728f0 Shannon Nelson 2021-03-10  172  
08f2e4b2b2008ce Shannon Nelson 2019-10-23  173  		i--;
08f2e4b2b2008ce Shannon Nelson 2019-10-23  174  	} while (i > 0);
08f2e4b2b2008ce Shannon Nelson 2019-10-23  175  
08f2e4b2b2008ce Shannon Nelson 2019-10-23  176  	return skb;
0f3154e6bcb3549 Shannon Nelson 2019-09-03  177  }
0f3154e6bcb3549 Shannon Nelson 2019-09-03  178  

:::::: The code at line 149 was first introduced by commit
:::::: 4b0a7539a3728f0fd7a11087d64371e8c28b4723 ionic: implement Rx page reuse

:::::: TO: Shannon Nelson <snelson@pensando.io>
:::::: CC: David S. Miller <davem@davemloft.net>

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

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