From ff589551c8e8e9e95e211b9d8daafb4ed39f1aec Mon Sep 17 00:00:00 2001 From: Prasad J Pandit Date: Mon, 6 Jun 2016 22:04:43 +0530 Subject: [PATCH] scsi: esp: check TI buffer index before read/write 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. Three control variables 'ti_rptr', 'ti_wptr' and 'ti_size' are used to control r/w access to the information transfer buffer ti_buf[TI_BUFSZ=16]. In that, 'ti_rptr' is used as read index, where read occurs. 'ti_wptr' is a write index, where write would occur. 'ti_size' indicates total bytes to be read from the buffer. While reading/writing to this buffer, index could exceed its size. Add check to avoid OOB r/w access. Reported-by: Huawei PSIRT Reported-by: Li Qiang Signed-off-by: Prasad J Pandit Message-Id: <1465230883-22303-1-git-send-email-ppandit@redhat.com> Signed-off-by: Paolo Bonzini --- hw/scsi/esp.c | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-) diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c index 591c8172d5..3adb685177 100644 --- a/hw/scsi/esp.c +++ b/hw/scsi/esp.c @@ -400,19 +400,17 @@ uint64_t esp_reg_read(ESPState *s, uint32_t saddr) trace_esp_mem_readb(saddr, s->rregs[saddr]); switch (saddr) { case ESP_FIFO: - if (s->ti_size > 0) { + if ((s->rregs[ESP_RSTAT] & STAT_PIO_MASK) == 0) { + /* Data out. */ + qemu_log_mask(LOG_UNIMP, "esp: PIO data read not implemented\n"); + s->rregs[ESP_FIFO] = 0; + esp_raise_irq(s); + } else if (s->ti_rptr < s->ti_wptr) { s->ti_size--; - if ((s->rregs[ESP_RSTAT] & STAT_PIO_MASK) == 0) { - /* Data out. */ - qemu_log_mask(LOG_UNIMP, - "esp: PIO data read not implemented\n"); - s->rregs[ESP_FIFO] = 0; - } else { - s->rregs[ESP_FIFO] = s->ti_buf[s->ti_rptr++]; - } + s->rregs[ESP_FIFO] = s->ti_buf[s->ti_rptr++]; esp_raise_irq(s); } - if (s->ti_size == 0) { + if (s->ti_rptr == s->ti_wptr) { s->ti_rptr = 0; s->ti_wptr = 0; } @@ -456,7 +454,7 @@ 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++; -- 2.11.4.GIT