Fix tulip breakage

The tulip network driver in a qemu-system-hppa emulation is broken in
the sense that bigger network packages aren't received any longer and
thus even running e.g. "apt update" inside the VM fails.

The breakage was introduced by commit 8ffb7265af ("check frame size and
r/w data length") which added checks to prevent accesses outside of the
rx/tx buffers.

But the new checks were implemented wrong. The variable rx_frame_len
counts backwards, from rx_frame_size down to zero, and the variable len
is never bigger than rx_frame_len, so accesses just can't happen and the
checks are unnecessary.
On the contrary the checks now prevented bigger packages to be moved
into the rx buffers.

This patch reverts the wrong checks and were sucessfully tested with a
qemu-system-hppa emulation.

Fixes: 8ffb7265af ("check frame size and r/w data length")
Buglink: https://bugs.launchpad.net/bugs/1874539
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Jason Wang <jasowang@redhat.com>
(cherry picked from commit d9b69640391618045949f7c500b87fc129f862ed)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/hw/net/tulip.c b/hw/net/tulip.c
index 1167c1bb07d74783f3fa47b01996a228a309cfee..c6654a98a9957505cc55fa45a586162a8c4a583a 100644 (file)
--- a/hw/net/tulip.c
+++ b/hw/net/tulip.c
@@ -171,9 +171,6 @@ static void tulip_copy_rx_bytes(TULIPState *s, struct tulip_descriptor *desc)
             len = s->rx_frame_len;
         }
 
-        if (s->rx_frame_len + len > sizeof(s->rx_frame)) {
-            return;
-        }
         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;
@@ -186,9 +183,6 @@ static void tulip_copy_rx_bytes(TULIPState *s, struct tulip_descriptor *desc)
             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;