* re: mm: add NR_ZSMALLOC to vmstat
@ 2016-06-06 20:05 Dan Carpenter
2016-06-07 2:21 ` Minchan Kim
0 siblings, 1 reply; 2+ messages in thread
From: Dan Carpenter @ 2016-06-06 20:05 UTC (permalink / raw)
To: minchan; +Cc: Sergey Senozhatsky, linux-mm
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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^ permalink raw reply [flat|nested] 2+ messages in thread* Re: mm: add NR_ZSMALLOC to vmstat
2016-06-06 20:05 mm: add NR_ZSMALLOC to vmstat Dan Carpenter
@ 2016-06-07 2:21 ` Minchan Kim
0 siblings, 0 replies; 2+ messages in thread
From: Minchan Kim @ 2016-06-07 2:21 UTC (permalink / raw)
To: Dan Carpenter; +Cc: Sergey Senozhatsky, linux-mm
Hello Dan,
On Mon, Jun 06, 2016 at 11:05:38PM +0300, Dan Carpenter wrote:
> 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.
Strictly speaking, it shouldn't be a problem because zone bit encoded
in page->flags is never changed although it is freed but I admit its'
not good pracice. I will send fix.
Thanks!
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