------------------------------------------------------------------------
*From*: 	P J P
*Subject*: 	[Qemu-devel] [PATCH 1/2] scsi: check command buffer length
before write(CVE-2016-4439)
*Date*: 	Thu, 19 May 2016 16:09:30 +0530

------------------------------------------------------------------------

From: Prasad J Pandit <address@hidden>

The 53C9X Fast SCSI Controller(FSC) comes with an internal 16-byte
FIFO buffer. It is used to handle command and data transfer. While
writing to this command buffer 's->cmdbuf[TI_BUFSZ=16]', a check
was missing to validate input length. Add check to avoid OOB write
access.

Fixes CVE-2016-4439
Reported-by: Li Qiang <address@hidden>

Signed-off-by: Prasad J Pandit <address@hidden>
---
 hw/scsi/esp.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/qemu-xen/hw/scsi/esp.c b/tools/qemu-xen/hw/scsi/esp.c
index 8961be2..01497e6 100644
--- a/tools/qemu-xen/hw/scsi/esp.c
+++ b/tools/qemu-xen/hw/scsi/esp.c
@@ -448,7 +448,11 @@ void esp_reg_write(ESPState *s, uint32_t saddr, uint64_t val)
         break;
     case ESP_FIFO:
         if (s->do_cmd) {
-            s->cmdbuf[s->cmdlen++] = val & 0xff;
+            if (s->cmdlen < TI_BUFSZ) {
+                s->cmdbuf[s->cmdlen++] = val & 0xff;
+            } else {
+                trace_esp_error_fifo_overrun();
+            }
         } else if (s->ti_size == TI_BUFSZ - 1) {
             trace_esp_error_fifo_overrun();
         } else {
-- 
2.5.5