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    Subject[PATCH 4.18 120/228] staging: pi433: fix race condition in pi433_ioctl
    Date
    4.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Hugo Lefeuvre <hle@owl.eu.com>

    [ Upstream commit 6de4ef65a8c6f53ce7eef06666410bc3b6e4b624 ]

    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 and simpler code.

    Signed-off-by: Hugo Lefeuvre <hle@owl.eu.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/staging/pi433/pi433_if.c | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    --- 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 retval = 0;
    struct pi433_instance *instance;
    struct pi433_device *device;
    + struct pi433_tx_cfg tx_cfg;
    void __user *argp = (void __user *)arg;

    /* Check type and command number */
    @@ -902,9 +903,11 @@ pi433_ioctl(struct file *filp, unsigned
    return -EFAULT;
    break;
    case PI433_IOC_WR_TX_CFG:
    - if (copy_from_user(&instance->tx_cfg, argp,
    - sizeof(struct pi433_tx_cfg)))
    + if (copy_from_user(&tx_cfg, argp, sizeof(struct pi433_tx_cfg)))
    return -EFAULT;
    + mutex_lock(&device->tx_fifo_lock);
    + memcpy(&instance->tx_cfg, &tx_cfg, sizeof(struct pi433_tx_cfg));
    + mutex_unlock(&device->tx_fifo_lock);
    break;
    case PI433_IOC_RD_RX_CFG:
    if (copy_to_user(argp, &device->rx_cfg,

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