netdev - [PATCH bpf] xdp: Prevent overflow in devmap_hash cost calculation for 32-bit builds

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Message-Id: <20191017105702.2807093-1-toke@redhat.com>
Date:   Thu, 17 Oct 2019 12:57:02 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     daniel@...earbox.net, ast@...com
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        bpf@...r.kernel.org, netdev@...r.kernel.org,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Subject: [PATCH bpf] 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@...ove.sakura.ne.jp>
Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
 kernel/bpf/devmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index a0a1153da5ae..e34fac6022eb 100644
--- 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 */
-- 
2.23.0