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scsi: esp: check TI buffer index before read/write

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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 <psirt@huawei.com>
Reported-by: Li Qiang <liqiang6-s@360.cn>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Message-Id: <1465230883-22303-1-git-send-email-ppandit@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Prasad J Pandit 2016-06-06 22:04:43 +05:30 committed by Paolo Bonzini
parent 4b3eec91b9
commit ff589551c8
1 changed files with 9 additions and 11 deletions
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20
hw/scsi/esp.c
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@ -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++;