The snprintf() function can return a length greater than the given
input size. That will require a check for buffer overrun after each
invocation of snprintf(). scnprintf(), on the other hand, will never
return a greater length. By using scnprintf() in selected places, we
can avoid some buffer overrun checks except after stack_depot_snprint()
and after the last snprintf().
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
mm/page_owner.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 99e360df9465..28dac73e0542 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -338,19 +338,16 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
if (!kbuf)
return -ENOMEM;
- ret = snprintf(kbuf, count,
+ ret = scnprintf(kbuf, count,
"Page allocated via order %u, mask %#x(%pGg), pid %d, ts %llu ns, free_ts %llu ns\n",
page_owner->order, page_owner->gfp_mask,
&page_owner->gfp_mask, page_owner->pid,
page_owner->ts_nsec, page_owner->free_ts_nsec);
- if (ret >= count)
- goto err;
-
/* Print information relevant to grouping pages by mobility */
pageblock_mt = get_pageblock_migratetype(page);
page_mt = gfp_migratetype(page_owner->gfp_mask);
- ret += snprintf(kbuf + ret, count - ret,
+ ret += scnprintf(kbuf + ret, count - ret,
"PFN %lu type %s Block %lu type %s Flags %pGp\n",
pfn,
migratetype_names[page_mt],
@@ -358,19 +355,14 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
migratetype_names[pageblock_mt],
&page->flags);
- if (ret >= count)
- goto err;
-
ret += stack_depot_snprint(handle, kbuf + ret, count - ret, 0);
if (ret >= count)
goto err;
if (page_owner->last_migrate_reason != -1) {
- ret += snprintf(kbuf + ret, count - ret,
+ ret += scnprintf(kbuf + ret, count - ret,
"Page has been migrated, last migrate reason: %s\n",
migrate_reason_names[page_owner->last_migrate_reason]);
- if (ret >= count)
- goto err;
}
ret += snprintf(kbuf + ret, count - ret, "\n");
--
2.27.0
