From: Peter Maydell <[email protected]> In commits like 969e50b61a28 ("net: Pad short frames to minimum size before sending from SLiRP/TAP") we switched away from requiring network devices to handle short frames to instead having the net core code do the padding of short frames out to the ETH_ZLEN minimum size. We then dropped the code for handling short frames from the network devices in a series of commits like 140eae9c8f7 ("hw/net: e1000: Remove the logic of padding short frames in the receive path").
This missed one route where the device's receive code can still see a short frame: if the device is in loopback mode and it transmits a short frame via the qemu_receive_packet() function, this will be fed back into its own receive code without being padded. Add the padding logic to qemu_receive_packet(). This fixes a buffer overrun which can be triggered in the e1000_receive_iov() logic via the loopback code path. Other devices that use qemu_receive_packet() to implement loopback are cadence_gem, dp8393x, lan9118, msf2-emac, pcnet, rtl8139 and sungem. Cc: [email protected] Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3043 Reviewed-by: Akihiko Odaki <[email protected]> Signed-off-by: Peter Maydell <[email protected]> Signed-off-by: Jason Wang <[email protected]> --- net/net.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/net/net.c b/net/net.c index 27e0d27807..8aefdb3424 100644 --- a/net/net.c +++ b/net/net.c @@ -775,10 +775,20 @@ ssize_t qemu_send_packet(NetClientState *nc, const uint8_t *buf, int size) ssize_t qemu_receive_packet(NetClientState *nc, const uint8_t *buf, int size) { + uint8_t min_pkt[ETH_ZLEN]; + size_t min_pktsz = sizeof(min_pkt); + if (!qemu_can_receive_packet(nc)) { return 0; } + if (net_peer_needs_padding(nc)) { + if (eth_pad_short_frame(min_pkt, &min_pktsz, buf, size)) { + buf = min_pkt; + size = min_pktsz; + } + } + return qemu_net_queue_receive(nc->incoming_queue, buf, size); } -- 2.42.0
