In the case where a SCSI layer transfer is incorrectly terminated, it is possible for a TI command to cause a SCSI buffer overflow due to the expected transfer data length being less than the available data in the FIFO. When this occurs the unsigned async_len variable underflows and becomes a large offset which writes past the end of the allocated SCSI buffer.
Restrict the non-DMA transfer length to be the smallest of the expected transfer length and the available FIFO data to ensure that it is no longer possible for the SCSI buffer overflow to occur. Signed-off-by: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1810 --- hw/scsi/esp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c index 4218a6a960..9b11d8c573 100644 --- a/hw/scsi/esp.c +++ b/hw/scsi/esp.c @@ -759,7 +759,8 @@ static void esp_do_nodma(ESPState *s) } if (to_device) { - len = MIN(fifo8_num_used(&s->fifo), ESP_FIFO_SZ); + len = MIN(s->async_len, ESP_FIFO_SZ); + len = MIN(len, fifo8_num_used(&s->fifo)); esp_fifo_pop_buf(&s->fifo, s->async_buf, len); s->async_buf += len; s->async_len -= len; -- 2.39.2
