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m25p80: don't let rogue SPI controllers cause buffer overruns

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In normal operation we should never attempt to put more
data into the data[] array than it can hold. However if the
SPI controller connected to us misbehaves then it can send
us a sequence of commands that attempt this. Since the
controller might be in the guest (if the hardware does SPI
via bit-banging), catch the possible overrun conditions and
reset the flash internal state, logging them as guest errors.

Signed-off-by: Jean-Christophe Dubois <jcd@tribudubois.net>
Message-id: 20170107111631.24444-1-jcd@tribudubois.net
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[PMM: rewrote commit message to be more exact about when
 this can happen]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Jean-Christophe Dubois 2017-01-09 11:40:23 +00:00 committed by Peter Maydell
parent 8dd845d3c4
commit 24cb2e0d57
1 changed files with 27 additions and 2 deletions
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29
hw/block/m25p80.c
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@ -28,6 +28,7 @@
#include "hw/ssi/ssi.h"
#include "qemu/bitops.h"
#include "qemu/log.h"
#include "qemu/error-report.h"
#include "qapi/error.h"
#ifndef M25P80_ERR_DEBUG
@ -377,6 +378,8 @@ typedef enum {
MAN_GENERIC,
} Manufacturer;
#define M25P80_INTERNAL_DATA_BUFFER_SZ 16
typedef struct Flash {
SSISlave parent_obj;
@ -387,7 +390,7 @@ typedef struct Flash {
int page_size;
uint8_t state;
uint8_t data[16];
uint8_t data[M25P80_INTERNAL_DATA_BUFFER_SZ];
uint32_t len;
uint32_t pos;
uint8_t needed_bytes;
@ -1115,6 +1118,17 @@ static uint32_t m25p80_transfer8(SSISlave *ss, uint32_t tx)
case STATE_COLLECTING_DATA:
case STATE_COLLECTING_VAR_LEN_DATA:
if (s->len >= M25P80_INTERNAL_DATA_BUFFER_SZ) {
qemu_log_mask(LOG_GUEST_ERROR,
"M25P80: Write overrun internal data buffer. "
"SPI controller (QEMU emulator or guest driver) "
"is misbehaving\n");
s->len = s->pos = 0;
s->state = STATE_IDLE;
break;
}
s->data[s->len] = (uint8_t)tx;
s->len++;
@ -1124,6 +1138,17 @@ static uint32_t m25p80_transfer8(SSISlave *ss, uint32_t tx)
break;
case STATE_READING_DATA:
if (s->pos >= M25P80_INTERNAL_DATA_BUFFER_SZ) {
qemu_log_mask(LOG_GUEST_ERROR,
"M25P80: Read overrun internal data buffer. "
"SPI controller (QEMU emulator or guest driver) "
"is misbehaving\n");
s->len = s->pos = 0;
s->state = STATE_IDLE;
break;
}
r = s->data[s->pos];
s->pos++;
if (s->pos == s->len) {
@ -1196,7 +1221,7 @@ static const VMStateDescription vmstate_m25p80 = {
.pre_save = m25p80_pre_save,
.fields = (VMStateField[]) {
VMSTATE_UINT8(state, Flash),
VMSTATE_UINT8_ARRAY(data, Flash, 16),
VMSTATE_UINT8_ARRAY(data, Flash, M25P80_INTERNAL_DATA_BUFFER_SZ),
VMSTATE_UINT32(len, Flash),
VMSTATE_UINT32(pos, Flash),
VMSTATE_UINT8(needed_bytes, Flash),