From 429f228f66b3dec61e2a12a826b2a48b98a5572c Mon Sep 17 00:00:00 2001

From: Jason Wang <jasowang@redhat.com>

Date: Wed, 8 May 2019 23:20:17 -0400

Subject: [PATCH 2/2] tuntap: fix dividing by zero in ebpf queue selection

Git-commit: a35d310f03a692bf4798eb309a1950a06a150620

Patch-mainline: v5.2-rc1

References: git-fixes

We need check if tun->numqueues is zero (e.g for the persist device)

before trying to use it for modular arithmetic.

Reported-by: Eric Dumazet <eric.dumazet@gmail.com>

Fixes: 96f84061620c6("tun: add eBPF based queue selection method")

Signed-off-by: Jason Wang <jasowang@redhat.com>

Reviewed-by: Eric Dumazet <edumazet@google.com>

Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Denis Kirjanov <denis.kirjanov@suse.com>

---

 drivers/net/tun.c | 7 ++++++-

 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c

index ac50b45c3629..85e957e2663c 100644

--- a/drivers/net/tun.c

+++ b/drivers/net/tun.c

@@ -591,13 +591,18 @@ static u16 tun_automq_select_queue(struct tun_struct *tun, struct sk_buff *skb)

 static u16 tun_ebpf_select_queue(struct tun_struct *tun, struct sk_buff *skb)

 {

 	struct tun_prog *prog;

+	u32 numqueues;

 	u16 ret = 0;

+	numqueues = READ_ONCE(tun->numqueues);

+	if (!numqueues)

+		return 0;

+

 	prog = rcu_dereference(tun->steering_prog);

 	if (prog)

 		ret = bpf_prog_run_clear_cb(prog->prog, skb);

-	return ret % tun->numqueues;

+	return ret % numqueues;

 }

 static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb,

-- 

2.16.4