From e855a6ec516b38d60a9a69b2ba4a88d720a97f97 Mon Sep 17 00:00:00 2001 From: Mark Cave-Ayland Date: Wed, 13 Sep 2023 21:44:09 +0100 Subject: [PATCH] esp: restrict non-DMA transfer length to that of available data 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 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1810 Reviewed-by: Thomas Huth Message-ID: <20230913204410.65650-3-mark.cave-ayland@ilande.co.uk> Signed-off-by: Paolo Bonzini (cherry picked from commit 77668e4b9bca03a856c27ba899a2513ddf52bb52) Signed-off-by: Michael Tokarev --- 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 4218a6a9605..9b11d8c5738 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; -- 2.39.5