From 3ebc439761273274ea00258da84d997841f01e72 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Thu, 24 Mar 2022 18:09:05 -0700 Subject: mm/page_owner: use scnprintf() to avoid excessive buffer overrun check 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(). Link: https://lkml.kernel.org/r/20220202203036.744010-3-longman@redhat.com Signed-off-by: Waiman Long Acked-by: David Rientjes Reviewed-by: Sergey Senozhatsky Acked-by: Rafael Aquini Acked-by: Mike Rapoport Cc: Andy Shevchenko Cc: Ira Weiny Cc: Johannes Weiner Cc: Michal Hocko Cc: Petr Mladek Cc: Rasmus Villemoes Cc: Roman Gushchin Cc: Steven Rostedt (Google) Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_owner.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-) (limited to 'mm/page_owner.c') 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"); -- cgit v1.2.3