[Qemu-devel] [PATCH] scsi: esp: check TI buffer index before read/write

[P J P <ppandit@redhat.com>]

From: Prasad J Pandit <pjp@fedoraproject.org>

The 53C9X Fast SCSI Controller(FSC) comes with internal 16-byte
FIFO buffers. One is used to handle commands and other is for
information transfer. While reading/writing to these buffers
an index into 's->ti_buf[TI_BUFSZ=16]' could exceed its size,
as a check was missing to validate it. Add check to avoid OOB
r/w access.

Reported-by: Huawei PSIRT <PSIRT@huawei.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/scsi/esp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index 591c817..80e4287 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -407,8 +407,10 @@ uint64_t esp_reg_read(ESPState *s, uint32_t saddr)
                 qemu_log_mask(LOG_UNIMP,
                               "esp: PIO data read not implemented\n");
                 s->rregs[ESP_FIFO] = 0;
-            } else {
+            } else if (s->ti_rptr < TI_BUFSZ) {
                 s->rregs[ESP_FIFO] = s->ti_buf[s->ti_rptr++];
+            } else {
+                trace_esp_error_fifo_overrun();
             }
             esp_raise_irq(s);
         }
@@ -456,7 +458,7 @@ void esp_reg_write(ESPState *s, uint32_t saddr, uint64_t val)
             } else {
                 trace_esp_error_fifo_overrun();
             }
-        } else if (s->ti_size == TI_BUFSZ - 1) {
+        } else if (s->ti_wptr == TI_BUFSZ - 1) {
             trace_esp_error_fifo_overrun();
         } else {
             s->ti_size++;
-- 
2.5.5