From: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Date: Wed, 7 Apr 2021 19:57:58 +0000 (+0100)
Subject: esp: don't overflow cmdfifo if TC is larger than the cmdfifo size
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=0ebb5fd80589835153a0c2baa1b8cc7a04e67a93;p=qemu.git

esp: don't overflow cmdfifo if TC is larger than the cmdfifo size

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>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <20210407195801.685-10-mark.cave-ayland@ilande.co.uk>
---

diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index 9d3fdb4398..a26a109166 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -578,6 +578,7 @@ 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 {