Hello Minchan Kim,
The patch b37284200b39: "mm: add NR_ZSMALLOC to vmstat" from Jun 5,
2016, leads to the following static checker warning:
mm/zsmalloc.c:1155 alloc_zspage()
error: we previously assumed 'page' could be null (see line 1152)
mm/zsmalloc.c
1130 /*
1131 * Allocate a zspage for the given size class
1132 */
1133 static struct zspage *alloc_zspage(struct zs_pool *pool,
1134 struct size_class *class,
1135 gfp_t gfp)
1136 {
1137 int i;
1138 struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE];
1139 struct zspage *zspage = cache_alloc_zspage(pool, gfp);
1140
1141 if (!zspage)
1142 return NULL;
1143
1144 memset(zspage, 0, sizeof(struct zspage));
1145 zspage->magic = ZSPAGE_MAGIC;
1146 migrate_lock_init(zspage);
1147
1148 for (i = 0; i < class->pages_per_zspage; i++) {
1149 struct page *page;
1150
1151 page = alloc_page(gfp);
1152 if (!page) {
^^^^
1153 while (--i >= 0) {
1154 __free_page(pages[i]);
1155 dec_zone_page_state(page, NR_ZSMALLOC);
^^^^
Potential NULL deref inside function call.
1156 }
1157 cache_free_zspage(pool, zspage);
1158 return NULL;
1159 }
1160
1161 inc_zone_page_state(page, NR_ZSMALLOC);
1162 pages[i] = page;
1163 }
1164
1165 create_page_chain(class, zspage, pages);
1166 init_zspage(class, zspage);
1167
1168 return zspage;
1169 }
regards,
dan carpenter
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