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Subject[PATCH net V3 1/2] tuntap: fix dividing by zero in ebpf queue selection
Date
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>
---
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 e9ca1c0..dc62fc3 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -596,13 +596,18 @@ 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,
--
1.8.3.1
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