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

[Jason Wang <jasowang@redhat.com>]

On 12/09/2015 11:28 PM, P J P wrote:
>    Hello Jason, Dmitry,
>
> +-- On Tue, 8 Dec 2015, P J P wrote --+
> | |1) VMXNET3_CMD_QUIESCE_DEV
> | 
> |   IIUC, it is used to pause the device when the receiver end is unable to 
> | keee-up with the incoming flow. After a brief period, the operation could be 
> | resumed again.
> | 
> | |2) VMXNET3_REG_DSAL
> | 
> |    Shared memory between a driver and the device appears to be set in two 
> | steps. Firs low address, followed by the high address(VMXNET3_REG_DSAH). I 
> | guess 's->device_active' needs to be enabled again while setting the higher 
> | part of the address.
>
> Please see below another (tested)patch, it fixes the VMXNET3_CMD_QUIESCE_DEV 
> case above. It's not clear if the device would be initialised and active while 
> setting shared memory via VMXNET3_REG_DSAL/DSAH.

I think it's possible for attacker. Better wait for Dmitry's answer for
this.

>
> ===
> From 81c4ecb67635435f01397dc21210497e6420bdca Mon Sep 17 00:00:00 2001
> From: Prasad J Pandit <pjp@fedoraproject.org>
> Date: Wed, 9 Dec 2015 20:45:25 +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, resulting in memory leakage on the host.
> This memory leakage could also occur, if the device was paused
> during flow control and activated thereafter.
>
> Introduced a 'Pause' state for the vmxnet3 device to differentiate
> it from the earlier active and inactive states. One need not
> 'activate' the device to resume operation after pause.
>
> This patch adds a check to verify these device states and avoid
> memory leakage during activating the device.
>
> Reported-by: Qinghao Tang <luodalongde@gmail.com>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/net/vmxnet3.c | 43 +++++++++++++++++++++++++++++++++++--------
>  hw/net/vmxnet3.h |  6 ++++++
>  2 files changed, 41 insertions(+), 8 deletions(-)
>
> diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
> index 37373e5..be2c9e2 100644
> --- a/hw/net/vmxnet3.c
> +++ b/hw/net/vmxnet3.c
> @@ -1195,7 +1195,19 @@ static void vmxnet3_reset_mac(VMXNET3State *s)
>  static void vmxnet3_deactivate_device(VMXNET3State *s)
>  {
>      VMW_CBPRN("Deactivating vmxnet3...");
> -    s->device_active = false;
> +    s->device_active = VMXNET3_DEV_DEACTIVE;
> +}
> +
> +static void vmxnet3_pause_device(VMXNET3State *s)
> +{
> +    VMW_CBPRN("Pausing vmxnet3...");
> +    s->device_active = VMXNET3_DEV_PAUSE;
> +}
> +
> +static void vmxnet3_resume_device(VMXNET3State *s)
> +{
> +    VMW_CBPRN("Resuming vmxnet3...");
> +    s->device_active = VMXNET3_DEV_ACTIVE;
>  }
>  
>  static void vmxnet3_reset(VMXNET3State *s)
> @@ -1431,6 +1443,12 @@ static void vmxnet3_activate_device(VMXNET3State *s)
>          return;
>      }
>  
> +    /* Verify if device is active */
> +    if (s->device_active) {
> +        VMW_CFPRN("Vmxnet3 device is active");
> +        return;
> +    }

What if guest want to activate a paused device?

> +
>      vmxnet3_adjust_by_guest_type(s);
>      vmxnet3_update_features(s);
>      vmxnet3_update_pm_state(s);
> @@ -1566,7 +1584,7 @@ static void vmxnet3_activate_device(VMXNET3State *s)
>  
>      vmxnet3_reset_mac(s);
>  
> -    s->device_active = true;
> +    s->device_active = VMXNET3_DEV_ACTIVE;
>  }
>  
>  static void vmxnet3_handle_command(VMXNET3State *s, uint64_t cmd)
> @@ -1627,8 +1645,13 @@ 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");
> -        vmxnet3_deactivate_device(s);
> +        if (s->device_active & VMXNET3_DEV_ACTIVE) {
> +            VMW_CBPRN("Set: VMXNET3_CMD_QUIESCE_DEV - pause the device");
> +            vmxnet3_pause_device(s);
> +        } else if (s->device_active & VMXNET3_DEV_PAUSE) {
> +            VMW_CBPRN("Set: VMXNET3_CMD_QUIESCE_DEV - resume the device");
> +            vmxnet3_resume_device(s);
> +        }

Not sure this is the correct behavior. Is there a link to the spec?

>          break;
>  
>      case VMXNET3_CMD_GET_CONF_INTR:
> @@ -1652,12 +1675,16 @@ static uint64_t vmxnet3_get_command_status(VMXNET3State *s)
>  
>      switch (s->last_command) {
>      case VMXNET3_CMD_ACTIVATE_DEV:
> -        ret = (s->device_active) ? 0 : -1;
> +        ret = (s->device_active & VMXNET3_DEV_ACTIVE) ? 0 : -1;
>          VMW_CFPRN("Device active: %" PRIx64, ret);
>          break;
>  
> -    case VMXNET3_CMD_RESET_DEV:
>      case VMXNET3_CMD_QUIESCE_DEV:
> +        ret = (s->device_active & VMXNET3_DEV_PAUSE) ? 0 : -1;
> +        VMW_CFPRN("Device pause: %" PRIx64, ret);
> +        break;
> +
> +    case VMXNET3_CMD_RESET_DEV:
>      case VMXNET3_CMD_GET_QUEUE_STATUS:
>          ret = 0;
>          break;
> @@ -1741,7 +1768,7 @@ vmxnet3_io_bar1_write(void *opaque,
>           * shared address only after we get the high part
>           */
>          if (val == 0) {
> -            s->device_active = false;
> +            s->device_active = VMXNET3_DEV_DEACTIVE;
>          }
>          s->temp_shared_guest_driver_memory = val;
>          s->drv_shmem = 0;
> @@ -1863,7 +1890,7 @@ static int
>  vmxnet3_can_receive(NetClientState *nc)
>  {
>      VMXNET3State *s = qemu_get_nic_opaque(nc);
> -    return s->device_active &&
> +    return (s->device_active & VMXNET3_DEV_ACTIVE) &&
>             VMXNET_FLAG_IS_SET(s->link_status_and_speed, VMXNET3_LINK_STATUS_UP);
>  }
>  
> diff --git a/hw/net/vmxnet3.h b/hw/net/vmxnet3.h
> index f7006af..71a7861 100644
> --- a/hw/net/vmxnet3.h
> +++ b/hw/net/vmxnet3.h
> @@ -202,6 +202,12 @@ enum {
>      VMXNET3_CMD_GET_ADAPTIVE_RING_INFO                    /* 0xF00D0009 */
>  };
>  
> +enum {
> +    VMXNET3_DEV_DEACTIVE = 0x00,  /* device deactive */
> +    VMXNET3_DEV_ACTIVE = 0x01,    /* device active  */
> +    VMXNET3_DEV_PAUSE = 0x02      /* device pause */
> +};
> +
>  /* Adaptive Ring Info Flags */
>  #define VMXNET3_DISABLE_ADAPTIVE_RING 1
>