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An unchecked integer assignment in the CAN driver may result in a division-by-zero which would result in a kernel crash (denial of service).
Tested locally, builds fine.
An unchecked integer assignment in the CAN driver may result in a division-by-zero which would result in a kernel crash (denial of service).
The CAN driver `can_ioctl` function, shown below (drivers/can/can.c), receives commands from user processes. Its received arguments `cmd` and content of `arg` are under attacker's control. In the CAN driver, some `ioctl` commands are hardware specific and are processed by calling `dev_ioctl()`. Subsequently, depending on the hardware (STM32 or AT32), this function calls `fdcan_ioctl` or `at32can_ioctl`, as shown in the snippets that follow.
```c
static int can_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
FAR struct inode *inode = filep->f_inode;
FAR struct can_dev_s *dev = inode->i_private;
FAR struct can_reader_s *reader = filep->f_priv;
...
flags = enter_critical_section();
/* Handle built-in ioctl commands */
switch (cmd)
{
...
/* Not a "built-in" ioctl command.. perhaps it is unique to this
* lower-half, device driver. */
default:
{
ret = dev_ioctl(dev, cmd, arg);
}
break;
}
leave_critical_section(flags);
return ret;
}
```
There are a few instances where the user can trigger a kernel crash, caused by a division by zero on `CANIOC_SET_BITTIMING` command. On STM32 platforms (arch/arm/src/stm32/stm32_fdcan.c), while there is a `DEBUGASSERT` assertion for `bt->bt_baud`, the check does not cover value `0`.
```c
static const struct can_ops_s g_fdcanops =
{
...
.co_ioctl = fdcan_ioctl,
...
};
static int fdcan_ioctl(struct can_dev_s *dev, int cmd, unsigned long arg)
{
...
switch (cmd)
{
...
case CANIOC_SET_BITTIMING:
{
const struct canioc_bittiming_s *bt = (const struct canioc_bittiming_s *)arg;
uint32_t nbrp;
uint32_t ntseg1;
uint32_t ntseg2;
uint32_t nsjw;
uint32_t ie;
uint8_t state;
DEBUGASSERT(bt != NULL);
DEBUGASSERT(bt->bt_baud < STM32_FDCANCLK_FREQUENCY); // <- not valid
DEBUGASSERT(bt->bt_sjw > 0 && bt->bt_sjw <= 16);
DEBUGASSERT(bt->bt_tseg1 > 1 && bt->bt_tseg1 <= 64);
DEBUGASSERT(bt->bt_tseg2 > 0 && bt->bt_tseg2 <= 16);
/* Extract bit timing data */
ntseg1 = bt->bt_tseg1 - 1;
ntseg2 = bt->bt_tseg2 - 1;
nsjw = bt->bt_sjw - 1;
nbrp = (uint32_t)
( ((float) STM32_FDCANCLK_FREQUENCY /
((float)(ntseg1 + ntseg2 + 3) * (float)bt->bt_baud)) - 1 ); // <- div by 0
```
Similarly, another division by zero was found in Artery Technology AT32 (arch/arm/src/stm32/stm32_can.c) driver:
```c
static const struct can_ops_s g_canops =
{
...
.co_ioctl = at32can_ioctl,
...
};
static int at32can_ioctl(struct can_dev_s *dev, int cmd, unsigned long arg)
{
...
/* Handle the command */
switch (cmd)
{
...
case CANIOC_SET_BITTIMING:
{
const struct canioc_bittiming_s *bt = (const struct canioc_bittiming_s *)arg;
...
uint32_t tmp;
uint32_t regval;
DEBUGASSERT(bt != NULL);
DEBUGASSERT(bt->bt_baud < AT32_PCLK1_FREQUENCY); // <- not valid
DEBUGASSERT(bt->bt_sjw > 0 && bt->bt_sjw <= 4);
DEBUGASSERT(bt->bt_tseg1 > 0 && bt->bt_tseg1 <= 16);
DEBUGASSERT(bt->bt_tseg2 > 0 && bt->bt_tseg2 <= 8);
regval = at32can_getreg(priv, AT32_CAN_BTMG_OFFSET);
/* Extract bit timing data tmp is in clocks per bit time */
tmp = AT32_PCLK1_FREQUENCY / bt->bt_baud; // <- div by 0
```
Instances found are listed in the *Location* section below. They are not shown in detail to reduce the length of the issue.
Ensure the attacker-controlled data is properly validated before use, to stop division by zero situations. For instance:
```c
DEBUGASSERT(bt->bt_baud > 0 && bt->bt_baud < AT32_PCLK1_FREQUENCY);
```
* arch/arm/src/stm32/stm32_fdcan.c
* arch/arm/src/stm32/stm32_can.c
* arch/arm/src/sama5/sam_mcan.c
* arch/arm/src/at32/at32_can.c
* arch/arm/src/samv7/sam_mcan.c
* arch/arm/src/stm32f0l0g0/stm32_fdcan.c
* arch/arm/src/stm32f7/stm32_can.c
* arch/arm/src/stm32h5/stm32_fdcan.c
* arch/arm/src/stm32l4/stm32l4_can.c
* arch/arm/src/tiva/common/tiva_can.c
* drivers/can/mcp2515.c
Signed-off-by: Catalin Visinescu <catalin_visinescu@yahoo.com>
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|---|---|---|
| .. | ||
| 1wire | ||
| aie | ||
| analog | ||
| audio | ||
| bch | ||
| can | ||
| clk | ||
| contactless | ||
| coresight | ||
| crypto | ||
| devicetree | ||
| dma | ||
| dummy | ||
| eeprom | ||
| efuse | ||
| i2c | ||
| i2s | ||
| i3c | ||
| input | ||
| ioexpander | ||
| ipcc | ||
| lcd | ||
| leds | ||
| loop | ||
| math | ||
| misc | ||
| mmcsd | ||
| modem | ||
| motor | ||
| mtd | ||
| net | ||
| note | ||
| pci | ||
| pinctrl | ||
| pipes | ||
| power | ||
| rc | ||
| regmap | ||
| reset | ||
| rf | ||
| rpmsg | ||
| rptun | ||
| segger | ||
| sensors | ||
| serial | ||
| spi | ||
| syslog | ||
| thermal | ||
| timers | ||
| usbdev | ||
| usbhost | ||
| usbmisc | ||
| usbmonitor | ||
| usrsock | ||
| vhost | ||
| video | ||
| virtio | ||
| wireless | ||
| .gitignore | ||
| CMakeLists.txt | ||
| drivers_initialize.c | ||
| Kconfig | ||
| Makefile | ||