From 7d09facec7d0b39bf1e8642ceb9a8a70f80919e6 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 13 May 2014 16:09:36 +0100 Subject: hw/net/stellaris_enet: Restructure tx_fifo code to avoid buffer overrun The current tx_fifo code has a corner case where the guest can overrun the fifo buffer: if automatic CRCs are disabled we allow the guest to write the CRC word even if there isn't actually space for it in the FIFO. The datasheet is unclear about exactly how the hardware deals with this situation; the most plausible answer seems to be that the CRC word is just lost. Implement this fix by separating the "can we stuff another word in the FIFO" logic from the "should we transmit the packet now" check. This also moves us closer to the real hardware, which has a number of ways it can be configured to trigger sending the packet, some of which we don't implement. Signed-off-by: Peter Maydell Reviewed-by: Dr. David Alan Gilbert Cc: qemu-stable@nongnu.org (cherry picked from commit 5c10495ab1546d5d12b51a97817051e9ec98d0f6) Signed-off-by: Michael Roth --- hw/net/stellaris_enet.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'hw/net') diff --git a/hw/net/stellaris_enet.c b/hw/net/stellaris_enet.c index 9dd77f7..8a1d0d1 100644 --- a/hw/net/stellaris_enet.c +++ b/hw/net/stellaris_enet.c @@ -252,10 +252,12 @@ static void stellaris_enet_write(void *opaque, hwaddr offset, s->tx_fifo[s->tx_fifo_len++] = value >> 24; } } else { - s->tx_fifo[s->tx_fifo_len++] = value; - s->tx_fifo[s->tx_fifo_len++] = value >> 8; - s->tx_fifo[s->tx_fifo_len++] = value >> 16; - s->tx_fifo[s->tx_fifo_len++] = value >> 24; + if (s->tx_fifo_len + 4 <= ARRAY_SIZE(s->tx_fifo)) { + s->tx_fifo[s->tx_fifo_len++] = value; + s->tx_fifo[s->tx_fifo_len++] = value >> 8; + s->tx_fifo[s->tx_fifo_len++] = value >> 16; + s->tx_fifo[s->tx_fifo_len++] = value >> 24; + } if (s->tx_fifo_len >= s->tx_frame_len) { /* We don't implement explicit CRC, so just chop it off. */ if ((s->tctl & SE_TCTL_CRC) == 0) -- cgit v1.1