Re: [PATCH v2] net: tulip: check frame size and r/w data length

[Jason Wang]

On 2020/2/17 下午7:38, P J P wrote:
From: Prasad J Pandit <p...@fedoraproject.org>

Tulip network driver while copying tx/rx buffers does not check
frame size against r/w data length. This may lead to OOB buffer
access. Add check to avoid it.

Reported-by: Li Qiang <pangpei...@antfin.com>
Reported-by: Ziming Zhang <ezrak...@gmail.com>
Signed-off-by: Prasad J Pandit <p...@fedoraproject.org>
---
  hw/net/tulip.c | 19 +++++++++++++++++--
  1 file changed, 17 insertions(+), 2 deletions(-)

Update v2: retain earlier len[12] & s->rx_frame_len checks
   -> https://lists.gnu.org/archive/html/qemu-devel/2020-02/msg04160.html

diff --git a/hw/net/tulip.c b/hw/net/tulip.c
index cfac2719d3..ea4fd371e3 100644
--- a/hw/net/tulip.c
+++ b/hw/net/tulip.c
@@ -170,6 +170,10 @@ static void tulip_copy_rx_bytes(TULIPState *s, struct 
tulip_descriptor *desc)
          } else {
              len = s->rx_frame_len;
          }
+
+        if (s->rx_frame_len + len >= sizeof(s->rx_frame)) {
+            return;
+        }


What's the goal of this checking?


          pci_dma_write(&s->dev, desc->buf_addr1, s->rx_frame +
              (s->rx_frame_size - s->rx_frame_len), len);
          s->rx_frame_len -= len;
@@ -181,6 +185,10 @@ static void tulip_copy_rx_bytes(TULIPState *s, struct 
tulip_descriptor *desc)
          } else {
              len = s->rx_frame_len;
          }
+
+        if (s->rx_frame_len + len >= sizeof(s->rx_frame)) {
+            return;
+        }
          pci_dma_write(&s->dev, desc->buf_addr2, s->rx_frame +
              (s->rx_frame_size - s->rx_frame_len), len);
          s->rx_frame_len -= len;
@@ -227,7 +235,8 @@ static ssize_t tulip_receive(TULIPState *s, const uint8_t 
*buf, size_t size)
  
      trace_tulip_receive(buf, size);
  
-    if (size < 14 || size > 2048 || s->rx_frame_len || tulip_rx_stopped(s)) {
+    if (size < 14 || size > sizeof(s->rx_frame) - 4
+        || s->rx_frame_len || tulip_rx_stopped(s)) {
          return 0;


It's better to move those checks in .can_receive().


      }
  
@@ -558,7 +567,7 @@ static void tulip_tx(TULIPState *s, struct tulip_descriptor *desc)
          if ((s->csr[6] >> CSR6_OM_SHIFT) & CSR6_OM_MASK) {
              /* Internal or external Loopback */
              tulip_receive(s, s->tx_frame, s->tx_frame_len);
-        } else {
+        } else if (s->tx_frame_len < sizeof(s->tx_frame)) {


Should we use <= here?


              qemu_send_packet(qemu_get_queue(s->nic),
                  s->tx_frame, s->tx_frame_len);
          }
@@ -575,12 +584,18 @@ static void tulip_copy_tx_buffers(TULIPState *s, struct 
tulip_descriptor *desc)
      int len1 = (desc->control >> TDES1_BUF1_SIZE_SHIFT) & 
TDES1_BUF1_SIZE_MASK;
      int len2 = (desc->control >> TDES1_BUF2_SIZE_SHIFT) & 
TDES1_BUF2_SIZE_MASK;
  
+    if (s->tx_frame_len + len1 >= sizeof(s->tx_frame)) {
+        return;
+    }


I think it's better to add a return value here to make sure caller 
tulip_xmit_list_update() can exit the loop early


      if (len1) {
          pci_dma_read(&s->dev, desc->buf_addr1,
              s->tx_frame + s->tx_frame_len, len1);
          s->tx_frame_len += len1;
      }
  
+    if (s->tx_frame_len + len2 >= sizeof(s->tx_frame)) {
+        return;
+    }
      if (len2) {
          pci_dma_read(&s->dev, desc->buf_addr2,
              s->tx_frame + s->tx_frame_len, len2);


One more thing.

It looks to me there could be a user trigger-able infinite loop in 
tun_list_update() through always set TDES0_OWN in its descriptors?

Thanks