Hello Alexander Duyck,
The patch dc35dbeda3e0: "fib_trie: Add tnode struct as a container
for fields not needed in key_vector" from Mar 6, 2015, leads to the
following static checker warnings:
net/ipv4/fib_trie.c:330 leaf_new() warn: variable dereferenced before check 'kv' (see line 328)
net/ipv4/fib_trie.c:358 tnode_new() warn: variable dereferenced before check 'tnode' (see line 350)
net/ipv4/fib_trie.c:853 resize() error: we previously assumed 'tp' could be null (see line 835)
net/ipv4/fib_trie.c:1891 fib_trie_get_first() warn: variable dereferenced before check 't' (see line 1889)
net/ipv4/fib_trie.c
325 static struct key_vector *leaf_new(t_key key, struct fib_alias *fa)
326 {
327 struct tnode *kv = kmem_cache_alloc(trie_leaf_kmem, GFP_KERNEL);
328 struct key_vector *l = kv->kv;
^^^^^^
Deref.
329
330 if (!kv)
^^^
Check.
331 return NULL;
332
333 /* initialize key vector */
334 l->key = key;
335 l->pos = 0;
336 l->bits = 0;
337 l->slen = fa->fa_slen;
338
339 /* link leaf to fib alias */
340 INIT_HLIST_HEAD(&l->leaf);
341 hlist_add_head(&fa->fa_list, &l->leaf);
342
343 return l;
344 }
[ snip ]
833 while (should_inflate(tp, tn) && max_work) {
834 tp = inflate(t, tn);
835 if (!tp) {
^^^
Is NULL here.
836 #ifdef CONFIG_IP_FIB_TRIE_STATS
837 this_cpu_inc(stats->resize_node_skipped);
838 #endif
839 break;
840 }
841
842 max_work--;
843 tn = get_child(tp, cindex);
844 }
845
846 /* Return if at least one inflate is run */
847 if (max_work != MAX_WORK)
848 return node_parent(tn);
849
850 /* Halve as long as the number of empty children in this
851 * node is above threshold.
852 */
853 while (should_halve(tp, tn) && max_work) {
^^^^^^^^^^^
should_halve() used to check for NULL but now it dereferences
unconditionally.
854 tp = halve(t, tn);
855 if (!tp) {
856 #ifdef CONFIG_IP_FIB_TRIE_STATS
857 this_cpu_inc(stats->resize_node_skipped);
858 #endif
859 break;
860 }
861
862 max_work--;
863 tn = get_child(tp, cindex);
864 }
regards,
dan carpenters
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