------------------------------------------------------------------------ *From*: P J P *Subject*: [Qemu-devel] [PATCH v3] scsi: esp: check TI buffer index before read/write *Date*: Mon, 6 Jun 2016 22:04:43 +0530 ------------------------------------------------------------------------ From: Prasad J Pandit 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 --- hw/scsi/esp.c | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-) Update as per: -> https://lists.gnu.org/archive/html/qemu-devel/2016-06/msg01326.html diff --git a/tools/qemu-xen-traditional/hw/esp.c b/tools/qemu-xen-traditional/hw/esp.c index c2f6f8f..4b94bbc 100644 --- a/tools/qemu-xen-traditional/hw/esp.c +++ b/tools/qemu-xen-traditional/hw/esp.c @@ -403,18 +403,17 @@ uint64_t esp_reg_read(ESPState *s, uint32_t saddr) DPRINTF("read reg[%d]: 0x%2.2x\n", 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. */ + ESP_ERROR("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. */ - ESP_ERROR("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; } @@ -459,7 +457,7 @@ void esp_reg_write(ESPState *s, uint32_t saddr, uint64_t val) } else { ESP_ERROR("fifo overrun\n"); } - } else if (s->ti_size == TI_BUFSZ - 1) { + } else if (s->ti_wptr == TI_BUFSZ - 1) { ESP_ERROR("fifo overrun\n"); } else { s->ti_size++; -- 2.5.5