On Tue, Jun 12, 2018 at 09:47:41PM -0400, Hugo Lefeuvre wrote:

In the PI433_IOC_WR_TX_CFG case in pi433_ioctl, instance->tx_cfg is modified via

copy_from_user(&instance->tx_cfg, argp, sizeof(struct pi433_tx_cfg)))

without any kind of synchronization. In the case where two threads would execute this same command concurrently the tx_cfg field might enter in an inconsistent state.

Additionally: if ioctl(PI433_IOC_WR_TX_CFG) and write() execute concurrently the tx config might be modified while it is being copied to the fifo, resulting in potential data corruption.

Fix: Get instance->tx_cfg_lock before modifying tx config in the PI433_IOC_WR_TX_CFG case in pi433_ioctl.

Also, do not copy data directly from user space to instance->tx_cfg. Instead use a temporary buffer allowing future checks for correctness of copied data.

Signed-off-by: Hugo Lefeuvre <hle@owl.eu.com> --- Changes in v2: - Use device->tx_fifo_lock instead of introducing a new lock in instance. - Do not copy data directly from user space to instance->tx_cfg, instead use a temporary buffer allowing future checks for correctness of copied data. --- drivers/staging/pi433/pi433_if.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/pi433/pi433_if.c b/drivers/staging/pi433/pi433_if.c index b061f77dda41..3ec1ed01d04b 100644 --- a/drivers/staging/pi433/pi433_if.c +++ b/drivers/staging/pi433/pi433_if.c @@ -880,6 +880,7 @@ pi433_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) int retval = 0; struct pi433_instance *instance; struct pi433_device *device; + struct pi433_tx_cfg tx_cfg_buffer; void __user *argp = (void __user *)arg;

/* Check type and command number */ @@ -902,9 +903,15 @@ pi433_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) return -EFAULT; break; case PI433_IOC_WR_TX_CFG: - if (copy_from_user(&instance->tx_cfg, argp, - sizeof(struct pi433_tx_cfg))) + /* do not modify tx config while it is being copied to fifo */ + mutex_lock(&device->tx_fifo_lock); + if (copy_from_user(&tx_cfg_buffer, argp, + sizeof(struct pi433_tx_cfg))) { + mutex_unlock(&device->tx_fifo_lock); return -EFAULT; + } + memcpy(&instance->tx_cfg, &tx_cfg_buffer, sizeof(struct pi433_tx_cfg)); + mutex_unlock(&device->tx_fifo_lock);

The lock is only needed around the memcpy() and that makes the code a bit simpler as well. regards, dan carpenter