Re: [PATCH net-next] hv_netvsc: Fix book keeping of skb during batching process

[David Miller]

From: Haiyang Zhang 
Date: Mon, 25 Jan 2016 09:49:31 -0800

> Since eliminating send_completion_tid from struct hv_netvsc_packet, we
> haven't add proper book keeping for the skb of the batched packet. This
> patch fixes this issue and allows the previous skb is properly freed.
> Otherwise, a panic may happen.
> Thanks to Simon Xiao  for bisecting and analysis.
> 
> Signed-off-by: Haiyang Zhang 
> Reviewed-by: K. Y. Srinivasan 

Applied.

[PATCH net-next] hv_netvsc: Fix book keeping of skb during batching process

[Haiyang Zhang]

Since eliminating send_completion_tid from struct hv_netvsc_packet, we
haven't add proper book keeping for the skb of the batched packet. This
patch fixes this issue and allows the previous skb is properly freed.
Otherwise, a panic may happen.
Thanks to Simon Xiao  for bisecting and analysis.

Signed-off-by: Haiyang Zhang 
Reviewed-by: K. Y. Srinivasan 
---
 drivers/net/hyperv/hyperv_net.h |1 +
 drivers/net/hyperv/netvsc.c |   33 ++---
 2 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index f4130af..fcb92c0 100644
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -624,6 +624,7 @@ struct nvsp_message {
 #define RNDIS_PKT_ALIGN_DEFAULT 8
 
 struct multi_send_data {
+   struct sk_buff *skb; /* skb containing the pkt */
struct hv_netvsc_packet *pkt; /* netvsc pkt pending */
u32 count; /* counter of batched packets */
 };
diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 059fc52..ec313fc 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -841,6 +841,18 @@ static inline int netvsc_send_pkt(
return ret;
 }
 
+/* Move packet out of multi send data (msd), and clear msd */
+static inline void move_pkt_msd(struct hv_netvsc_packet **msd_send,
+   struct sk_buff **msd_skb,
+   struct multi_send_data *msdp)
+{
+   *msd_skb = msdp->skb;
+   *msd_send = msdp->pkt;
+   msdp->skb = NULL;
+   msdp->pkt = NULL;
+   msdp->count = 0;
+}
+
 int netvsc_send(struct hv_device *device,
struct hv_netvsc_packet *packet,
struct rndis_message *rndis_msg,
@@ -855,6 +867,7 @@ int netvsc_send(struct hv_device *device,
unsigned int section_index = NETVSC_INVALID_INDEX;
struct multi_send_data *msdp;
struct hv_netvsc_packet *msd_send = NULL, *cur_send = NULL;
+   struct sk_buff *msd_skb = NULL;
bool try_batch;
bool xmit_more = (skb != NULL) ? skb->xmit_more : false;
 
@@ -897,10 +910,8 @@ int netvsc_send(struct hv_device *device,
   net_device->send_section_size) {
section_index = netvsc_get_next_send_section(net_device);
if (section_index != NETVSC_INVALID_INDEX) {
-   msd_send = msdp->pkt;
-   msdp->pkt = NULL;
-   msdp->count = 0;
-   msd_len = 0;
+   move_pkt_msd(&msd_send, &msd_skb, msdp);
+   msd_len = 0;
}
}
 
@@ -919,31 +930,31 @@ int netvsc_send(struct hv_device *device,
packet->total_data_buflen += msd_len;
}
 
-   if (msdp->pkt)
-   dev_kfree_skb_any(skb);
+   if (msdp->skb)
+   dev_kfree_skb_any(msdp->skb);
 
if (xmit_more && !packet->cp_partial) {
+   msdp->skb = skb;
msdp->pkt = packet;
msdp->count++;
} else {
cur_send = packet;
+   msdp->skb = NULL;
msdp->pkt = NULL;
msdp->count = 0;
}
} else {
-   msd_send = msdp->pkt;
-   msdp->pkt = NULL;
-   msdp->count = 0;
+   move_pkt_msd(&msd_send, &msd_skb, msdp);
cur_send = packet;
}
 
if (msd_send) {
-   m_ret = netvsc_send_pkt(msd_send, net_device, pb, skb);
+   m_ret = netvsc_send_pkt(msd_send, net_device, NULL, msd_skb);
 
if (m_ret != 0) {
netvsc_free_send_slot(net_device,
  msd_send->send_buf_index);
-   dev_kfree_skb_any(skb);
+   dev_kfree_skb_any(msd_skb);
}
}
 
-- 
1.7.4.1