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[Qemu-devel] [PATCH 12/23] stellaris_enet: avoid buffer orerrun on incom

From: Michael S. Tsirkin
Subject: [Qemu-devel] [PATCH 12/23] stellaris_enet: avoid buffer orerrun on incoming migration (part 3)
Date: Tue, 3 Dec 2013 18:28:53 +0200

From: Michael Roth <address@hidden>


s->tx_frame_len is read from the wire and can later used as an index
into s->tx_fifo[] for memset() when a DATA command is issued by the guest.

In this case s->tx_frame_len is checked to avoid an overrun, but if the
value is negative a subsequently executed guest can underrun the buffer
with zeros via the memset() call.

Fix this by failing migration if the incoming value is of s->tx_frame_len
is less than -1 (the emulation code allows from -1 as a special case)

Signed-off-by: Michael Roth <address@hidden>
Signed-off-by: Michael S. Tsirkin <address@hidden>
 hw/net/stellaris_enet.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/net/stellaris_enet.c b/hw/net/stellaris_enet.c
index 65f0ba8..6eca31e 100644
--- a/hw/net/stellaris_enet.c
+++ b/hw/net/stellaris_enet.c
@@ -375,6 +375,9 @@ static int stellaris_enet_load(QEMUFile *f, void *opaque, 
int version_id)
     s->mrxd = qemu_get_be32(f);
     s->np = qemu_get_be32(f);
     s->tx_frame_len = qemu_get_be32(f);
+    if (s->tx_frame_len < -1) {
+        return -EINVAL;
+    }
     s->tx_fifo_len = qemu_get_be32(f);
     if (s->tx_fifo_len < 0 || s->tx_fifo_len > SE_FIFO_LEN) {
         return -EINVAL;

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