If the guest tries to read a CDB using DMA and cmdfifo is not empty then it is possible to overflow cmdfifo.
Since this can only occur by issuing deliberately incorrect instruction sequences, ensure that the maximum length of the CDB transferred to cmdfifo is limited to the available free space within cmdfifo. Buglink: https://bugs.launchpad.net/qemu/+bug/1909247 Signed-off-by: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk> Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org> Tested-by: Alexander Bulekov <alx...@bu.edu> --- hw/scsi/esp.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c index 7f49522e1d..53cc569e8a 100644 --- a/hw/scsi/esp.c +++ b/hw/scsi/esp.c @@ -243,6 +243,7 @@ static uint32_t get_cmd(ESPState *s, uint32_t maxlen) } if (s->dma_memory_read) { s->dma_memory_read(s->dma_opaque, buf, dmalen); + dmalen = MIN(fifo8_num_free(&s->cmdfifo), dmalen); fifo8_push_all(&s->cmdfifo, buf, dmalen); } else { if (esp_select(s) < 0) { @@ -262,6 +263,7 @@ static uint32_t get_cmd(ESPState *s, uint32_t maxlen) if (n >= 3) { buf[0] = buf[2] >> 5; } + n = MIN(fifo8_num_free(&s->cmdfifo), n); fifo8_push_all(&s->cmdfifo, buf, n); } trace_esp_get_cmd(dmalen, target); -- 2.20.1
