> -----Original Message-----
> From: devel [mailto:[email protected]] On
> Behalf Of K. Y. Srinivasan
> Sent: Tuesday, April 28, 2015 9:15
> To: [email protected]; [email protected]; linux-
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]
> Subject: [PATCH net 1/1] hv_netvsc: Fix a bug in netvsc_start_xmit()
> 
> Commit commit b08cc79155fc26d0d112b1470d1ece5034651a4b
> eliminated memory
> allocation in the packet send path. This commit introduced a bug since it
> did not account for the case if the skb was cloned. Fix this bug by
> using the pre-reserved head room only if the skb is not cloned.
> 
> Signed-off-by: K. Y. Srinivasan <[email protected]>
> ---
>  drivers/net/hyperv/netvsc_drv.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/net/hyperv/netvsc_drv.c
> b/drivers/net/hyperv/netvsc_drv.c
> index a3a9d38..7eb0251 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -421,7 +421,7 @@ check_size:
> 
>       pkt_sz = sizeof(struct hv_netvsc_packet) + RNDIS_AND_PPI_SIZE;
> 
> -     if (head_room < pkt_sz) {
> +     if (skb->cloned ||  head_room < pkt_sz) {
>               packet = kmalloc(pkt_sz, GFP_ATOMIC);
>               if (!packet) {
>                       /* out of memory, drop packet */
> --

Without the patch, the guest can panic due to memory corruption.

I confirm the patch can fix the panic I saw.

Tested-by: Dexuan Cui <[email protected]>

Thanks,
-- Dexuan
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