[PATCH 2/4] esp: don't overflow cmdfifo if TC is larger than the cmdfifo size

[Mark Cave-Ayland]

If a guest transfers the message out/command phase data using DMA with a TC
that is larger than the cmdfifo size then the cmdfifo overflows triggering
an assert. Limit the size of the transfer to the free space available in
cmdfifo.

Buglink: https://bugs.launchpad.net/qemu/+bug/1919036
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 hw/scsi/esp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index 5d3f1ccbc8..bbcbfa4a91 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -579,6 +579,7 @@ static void esp_do_dma(ESPState *s)
         cmdlen = fifo8_num_used(&s->cmdfifo);
         trace_esp_do_dma(cmdlen, len);
         if (s->dma_memory_read) {
+            len = MIN(len, fifo8_num_free(&s->cmdfifo));
             s->dma_memory_read(s->dma_opaque, buf, len);
             fifo8_push_all(&s->cmdfifo, buf, len);
         } else {
-- 
2.20.1