Re: [PATCH net -v2] [BUGFIX] bonding: use local function pointer of bond->recv_probe in bond_handle_frame

Eric Dumazet
2011-10-19T04:05:27Z

Le jeudi 13 octobre 2011 à 11:04 +0900, Mitsuo Hayasaka a écrit :
> The bond->recv_probe is called in bond_handle_frame() when
> a packet is received, but bond_close() sets it to NULL. So,
> a panic occurs when both functions work in parallel.
>
> Why this happen:
> After null pointer check of bond->recv_probe, an sk_buff is
> duplicated and bond->recv_probe is called in bond_handle_frame.
> So, a panic occurs when bond_close() is called between the
> check and call of bond->recv_probe.
>
> Patch:
> This patch uses a local function pointer of bond->recv_probe
> in bond_handle_frame(). So, it can avoid the null pointer
> dereference.
>
>
> Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
> Cc: Jay Vosburgh <fubar@us.ibm.com>
> Cc: Andy Gospodarek <andy@greyhouse.net>
> Cc: Eric Dumazet <eric.dumazet@gmail.com>
> Cc: WANG Cong <xiyou.wangcong@gmail.com>
> ---
>
> drivers/net/bonding/bond_main.c | 7 +++++--
> 1 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 6d79b78..de3d351 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -1435,6 +1435,8 @@ static rx_handler_result_t bond_handle_frame(struct sk_buff **pskb)
> struct sk_buff *skb = *pskb;
> struct slave *slave;
> struct bonding *bond;
> + void (*recv_probe)(struct sk_buff *, struct bonding *,
> + struct slave *);
>
> skb = skb_share_check(skb, GFP_ATOMIC);
> if (unlikely(!skb))
> @@ -1448,11 +1450,12 @@ static rx_handler_result_t bond_handle_frame(struct sk_buff **pskb)
> if (bond->params.arp_interval)
> slave->dev->last_rx = jiffies;
>
> - if (bond->recv_probe) {
> + recv_probe = ACCESS_ONCE(bond->recv_probe);
> + if (recv_probe) {
> struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
>
> if (likely(nskb)) {
> - bond->recv_probe(nskb, bond, slave);
> + recv_probe(nskb, bond, slave);
> dev_kfree_skb(nskb);
> }
> }
>

Sorry, I forgot to add my official ack. Even if not a perfect patch, its
a step into right direction.

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