netdev - [PATCH bpf-next 3/4] libbpf: fix potential multiplication overflow in mmap() size calculation

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Date:   Thu, 16 Jan 2020 22:08:00 -0800
From:   Andrii Nakryiko <andriin@...com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
        <daniel@...earbox.net>
CC:     <andrii.nakryiko@...il.com>, <kernel-team@...com>,
        Andrii Nakryiko <andriin@...com>
Subject: [PATCH bpf-next 3/4] libbpf: fix potential multiplication overflow in mmap() size calculation

Prevent potential overflow performed in 32-bit integers, before assigning
result to size_t. Reported by LGTM static analysis.

Fixes: eba9c5f498a1 ("libbpf: Refactor global data map initialization")
Signed-off-by: Andrii Nakryiko <andriin@...com>
---
 tools/lib/bpf/libbpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 3b0b88c3377d..fc41c3f2e983 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1283,7 +1283,7 @@ static size_t bpf_map_mmap_sz(const struct bpf_map *map)
 	long page_sz = sysconf(_SC_PAGE_SIZE);
 	size_t map_sz;
 
-	map_sz = roundup(map->def.value_size, 8) * map->def.max_entries;
+	map_sz = (size_t)roundup(map->def.value_size, 8) * map->def.max_entries;
 	map_sz = roundup(map_sz, page_sz);
 	return map_sz;
 }
-- 
2.17.1