Re: [Qemu-devel] [PATCH 1/2] net: pcnet: check rx/tx descriptor ring length

[Jason Wang]

On 2016年09月30日 13:36, P J P wrote:

   Hello Jason,

+-- On Fri, 30 Sep 2016, Jason Wang wrote --+
| On 2016年09月30日 02:57, P J P wrote:
| > The AMD PC-Net II emulator has set of control and status(CSR)
| > registers. Of these, CSR76 and CSR78 hold receive and transmit
| > descriptor ring length respectively. This ring length could range
| > from 1 to 65535. Setting ring length to zero leads to an infinite
| > loop in pcnet_rdra_addr. Add check to avoid it.
|
| In this case, we only need to protect RCVRL I believe? (since XMTRL were not
| used).

   XMTRL is not used in this case, but could be prone to similar issues. For
ex.

 static void pcnet_transmit(PCNetState *s)
 {
 int count = CSR_XMTRL(s) - 1;
 ...
 if (count--)
 goto txagain;
 }

If CSR_XMTRL is set to zero(0), 'count' would never reach zero and function
would continue to jump to 'txagain'.


Applied and tweak the commit log by mentioning pcnet_transmit() too.

Thanks



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

Re: [Qemu-devel] [PATCH 1/2] net: pcnet: check rx/tx descriptor ring length

[P J P]

  Hello Jason,

+-- On Fri, 30 Sep 2016, Jason Wang wrote --+
| On 2016年09月30日 02:57, P J P wrote:
| > The AMD PC-Net II emulator has set of control and status(CSR)
| > registers. Of these, CSR76 and CSR78 hold receive and transmit
| > descriptor ring length respectively. This ring length could range
| > from 1 to 65535. Setting ring length to zero leads to an infinite
| > loop in pcnet_rdra_addr. Add check to avoid it.
| 
| In this case, we only need to protect RCVRL I believe? (since XMTRL were not
| used).

  XMTRL is not used in this case, but could be prone to similar issues. For 
ex.

static void pcnet_transmit(PCNetState *s)
{
int count = CSR_XMTRL(s) - 1;
...
if (count--)
goto txagain;
}

If CSR_XMTRL is set to zero(0), 'count' would never reach zero and function 
would continue to jump to 'txagain'.

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

Re: [Qemu-devel] [PATCH 1/2] net: pcnet: check rx/tx descriptor ring length

[Jason Wang]

On 2016年09月30日 02:57, P J P wrote:

From: Prasad J Pandit 

The AMD PC-Net II emulator has set of control and status(CSR)
registers. Of these, CSR76 and CSR78 hold receive and transmit
descriptor ring length respectively. This ring length could range
from 1 to 65535. Setting ring length to zero leads to an infinite
loop in pcnet_rdra_addr. Add check to avoid it.


In this case, we only need to protect RCVRL I believe? (since XMTRL were 
not used).




Reported-by: Li Qiang 
Signed-off-by: Prasad J Pandit 
---
  hw/net/pcnet.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/hw/net/pcnet.c b/hw/net/pcnet.c
index 198a01f..3078de8 100644
--- a/hw/net/pcnet.c
+++ b/hw/net/pcnet.c
@@ -1429,8 +1429,11 @@ static void pcnet_csr_writew(PCNetState *s, uint32_t 
rap, uint32_t new_value)
  case 47: /* POLLINT */
  case 72:
  case 74:
+break;
  case 76: /* RCVRL */
  case 78: /* XMTRL */
+val = (val > 0) ? val : 512;
+break;
  case 112:
 if (CSR_STOP(s) || CSR_SPND(s))
 break;

[Qemu-devel] [PATCH 1/2] net: pcnet: check rx/tx descriptor ring length

[P J P]

From: Prasad J Pandit 

The AMD PC-Net II emulator has set of control and status(CSR)
registers. Of these, CSR76 and CSR78 hold receive and transmit
descriptor ring length respectively. This ring length could range
from 1 to 65535. Setting ring length to zero leads to an infinite
loop in pcnet_rdra_addr. Add check to avoid it.

Reported-by: Li Qiang 
Signed-off-by: Prasad J Pandit 
---
 hw/net/pcnet.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/net/pcnet.c b/hw/net/pcnet.c
index 198a01f..3078de8 100644
--- a/hw/net/pcnet.c
+++ b/hw/net/pcnet.c
@@ -1429,8 +1429,11 @@ static void pcnet_csr_writew(PCNetState *s, uint32_t 
rap, uint32_t new_value)
 case 47: /* POLLINT */
 case 72:
 case 74:
+break;
 case 76: /* RCVRL */
 case 78: /* XMTRL */
+val = (val > 0) ? val : 512;
+break;
 case 112:
if (CSR_STOP(s) || CSR_SPND(s))
break;
-- 
2.5.5