xdp: Prevent overflow in devmap_hash cost calculation for 32-bit builds

Tetsuo pointed out that without an explicit cast, the cost calculation for
devmap_hash type maps could overflow on 32-bit builds. This adds the
missing cast.

Fixes: 6f9d451ab1a3 ("xdp: Add devmap_hash map type for looking up devices by hashed index")
Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20191017105702.2807093-1-toke@redhat.com

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index d27f3b6..c0a48f3 100644 (file)
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -128,7 +128,7 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
 
                if (!dtab->n_buckets) /* Overflow check */
                        return -EINVAL;
-               cost += sizeof(struct hlist_head) * dtab->n_buckets;
+               cost += (u64) sizeof(struct hlist_head) * dtab->n_buckets;
        }
 
        /* if map size is larger than memlock limit, reject it */