[qemu-xen staging] hw/net/net_tx_pkt: fix assertion failure in net_tx_pkt_add_raw_fragment()

[patchbot@xxxxxxx]

commit 035e69b063835a5fd23cacabd63690a3d84532a8
Author:     Mauro Matteo Cascella <mcascell@xxxxxxxxxx>
AuthorDate: Sat Aug 1 18:42:38 2020 +0200
Commit:     Jason Wang <jasowang@xxxxxxxxxx>
CommitDate: Tue Aug 4 14:14:48 2020 +0800

    hw/net/net_tx_pkt: fix assertion failure in net_tx_pkt_add_raw_fragment()
    
    An assertion failure issue was found in the code that processes network 
packets
    while adding data fragments into the packet context. It could be abused by a
    malicious guest to abort the QEMU process on the host. This patch replaces 
the
    affected assert() with a conditional statement, returning false if the 
current
    data fragment exceeds max_raw_frags.
    
    Reported-by: Alexander Bulekov <alxndr@xxxxxx>
    Reported-by: Ziming Zhang <ezrakiez@xxxxxxxxx>
    Reviewed-by: Dmitry Fleytman <dmitry.fleytman@xxxxxxxxx>
    Signed-off-by: Mauro Matteo Cascella <mcascell@xxxxxxxxxx>
    Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
 hw/net/net_tx_pkt.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c
index 9560e4a49e..da262edc3e 100644
--- a/hw/net/net_tx_pkt.c
+++ b/hw/net/net_tx_pkt.c
@@ -379,7 +379,10 @@ bool net_tx_pkt_add_raw_fragment(struct NetTxPkt *pkt, 
hwaddr pa,
     hwaddr mapped_len = 0;
     struct iovec *ventry;
     assert(pkt);
-    assert(pkt->max_raw_frags > pkt->raw_frags);
+
+    if (pkt->raw_frags >= pkt->max_raw_frags) {
+        return false;
+    }
 
     if (!len) {
         return true;
--
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