Re: [Qemu-devel] net: vmxnet3: memory leakage issue

[Dmitry Fleytman]

Hello Prasad,

> On 14 Dec 2015, at 13:58 PM, P J P <address@hidden> wrote:
> 
>  Hello Dmitry, Jason
> 
> +-- On Sun, 13 Dec 2015, Dmitry Fleytman wrote --+
> | According to Linux driver code VMXNET3_CMD_QUIESCE_DEV does not flip 
> | paused/active states. It always disables device, see vmxnet3_resume() for 
> |
> | 
> <https://lxr.missinglinkelectronics.com/linux/drivers/net/vmxnet3/vmxnet3_drv.c#L3423>):
> | 
> | Driver issues VMXNET3_CMD_QUIESCE_DEV to clear the device state and then 
> | performs activate sequence to launch the device.
> 
>  Yes, I did look through it. But it wasn't clear how it does flow control. As 
> it resets the device on pause and loses any outstanding data. Whereas in the 
> vmxnet3 emulator, upon deactivation it merely sets the 's->active_device' 
> flag 
> to be false, and the same is checked before receiving new packets. Do either 
> of the vmxnet3 implementations perform flow control?(to avoid congestion)

It’s hard to say as spec is not available.

> 
> | So the correct fix should:
> | 
> | 1. On device activation: check if device is active - do nothing
> | 2. In all places that set device_active to false, i.e. device quiesce, 
> reset and VMXNET3_REG_DSAL set to zero: deallocate tx/rx packets as done in 
> vmxnet3_net_uninit():
> | 
> | net_tx_pkt_reset(s->tx_pkt);
> | net_tx_pkt_uninit(s->tx_pkt);
> | net_rx_pkt_uninit(s->rx_pkt);
> | 
> | It could be a good idea to extend vmxnet3_deactivate_device() with those 
> | lines and call it from every place that sets device_active to false or 
> frees 
> | TX/RX packets.
> 
>  Right. Please see below a new tested patch which does this and fixes the 
> host memory leakage issue. Does it look good?
> 
> ===
> From d4b277788d518e915cc6c20488d587cb5716e96a Mon Sep 17 00:00:00 2001
> From: Prasad J Pandit <address@hidden>
> Date: Mon, 14 Dec 2015 16:56:52 +0530
> Subject: [PATCH] net: vmxnet3: avoid memory leakage in activate_device
> 
> Vmxnet3 device emulator does not check if the device is active
> before activating it, also it did not free the transmit & receive
> buffers while deactivating the device, thus resulting in memory
> leakage on the host. This patch fixes both these issues to avoid
> host memory leakage.
> 
> Reported-by: Qinghao Tang <address@hidden>
> Signed-off-by: Prasad J Pandit <address@hidden>
> ---
> hw/net/vmxnet3.c | 18 ++++++++++++------
> 1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
> index 37373e5..3936f12 100644
> --- a/hw/net/vmxnet3.c
> +++ b/hw/net/vmxnet3.c
> @@ -1195,6 +1195,9 @@ static void vmxnet3_reset_mac(VMXNET3State *s)
> static void vmxnet3_deactivate_device(VMXNET3State *s)
> {
>     VMW_CBPRN("Deactivating vmxnet3...");
> +    vmxnet_tx_pkt_reset(s->tx_pkt);
> +    vmxnet_tx_pkt_uninit(s->tx_pkt);
> +    vmxnet_rx_pkt_uninit(s->rx_pkt);
>     s->device_active = false;
> }
> 
> @@ -1204,7 +1207,6 @@ static void vmxnet3_reset(VMXNET3State *s)
> 
>     vmxnet3_deactivate_device(s);
>     vmxnet3_reset_interrupt_states(s);
> -    vmxnet_tx_pkt_reset(s->tx_pkt);
>     s->drv_shmem = 0;
>     s->tx_sop = true;
>     s->skip_current_tx_pkt = false;
> @@ -1431,6 +1433,12 @@ static void vmxnet3_activate_device(VMXNET3State *s)
>         return;
>     }
> 
> +    /* Verify if device is active */
> +    if (s->device_active) {
> +        VMW_CFPRN("Vmxnet3 device is active");
> +        return;
> +    }
> +
>     vmxnet3_adjust_by_guest_type(s);
>     vmxnet3_update_features(s);
>     vmxnet3_update_pm_state(s);
> @@ -1627,7 +1635,7 @@ static void vmxnet3_handle_command(VMXNET3State *s, 
> uint64_t cmd)
>         break;
> 
>     case VMXNET3_CMD_QUIESCE_DEV:
> -        VMW_CBPRN("Set: VMXNET3_CMD_QUIESCE_DEV - pause the device");
> +        VMW_CBPRN("Set: VMXNET3_CMD_QUIESCE_DEV - deactivate the device");
>         vmxnet3_deactivate_device(s);
>         break;
> 
> @@ -1741,7 +1749,7 @@ vmxnet3_io_bar1_write(void *opaque,
>          * shared address only after we get the high part
>          */
>         if (val == 0) {
> -            s->device_active = false;
> +            vmxnet3_deactivate_device(s);
>         }
>         s->temp_shared_guest_driver_memory = val;
>         s->drv_shmem = 0;
> @@ -2021,9 +2029,7 @@ static bool vmxnet3_peer_has_vnet_hdr(VMXNET3State *s)
> static void vmxnet3_net_uninit(VMXNET3State *s)
> {
>     g_free(s->mcast_list);
> -    vmxnet_tx_pkt_reset(s->tx_pkt);
> -    vmxnet_tx_pkt_uninit(s->tx_pkt);
> -    vmxnet_rx_pkt_uninit(s->rx_pkt);
> +    vmxnet3_deactivate_device(s);
>     qemu_del_nic(s->nic);
> }

The patch looks basically good.
The only issue I can think of is that now vmxnet_tx_pkt_uninit and 
vmxnet_rx_pkt_uninit may be called a few times in a row. For example guest may 
quiesce device and then shutdown. In this case vmxnet_tx_pkt_uninit may try to 
free the same memory twice. Could you take a look at this please?

Thanks for working on this,
Dmitry

> 
> -- 
> 2.4.3
> ===
> 
> 
> Thank you.
> --
> Prasad J Pandit / Red Hat Product Security Team
> 47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F