From: Mauro Carvalho Chehab <[email protected]> commit da5516b5e81d45a96291823620f6c820178dc055 upstream
Two readonly ioctls can't be allowed if the frontend device is opened in read only mode. Explain why. Reviewed by: Shuah Khan <[email protected]> Signed-off-by: Mauro Carvalho Chehab <[email protected]> Signed-off-by: Florian Fainelli <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/media/dvb-core/dvb_frontend.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c index a7ba8e200b677..673cefb7230cb 100644 --- a/drivers/media/dvb-core/dvb_frontend.c +++ b/drivers/media/dvb-core/dvb_frontend.c @@ -1925,9 +1925,23 @@ static int dvb_frontend_ioctl(struct file *file, unsigned int cmd, void *parg) return -ENODEV; } - if ((file->f_flags & O_ACCMODE) == O_RDONLY && - (_IOC_DIR(cmd) != _IOC_READ || cmd == FE_GET_EVENT || - cmd == FE_DISEQC_RECV_SLAVE_REPLY)) { + /* + * If the frontend is opened in read-only mode, only the ioctls + * that don't interfere with the tune logic should be accepted. + * That allows an external application to monitor the DVB QoS and + * statistics parameters. + * + * That matches all _IOR() ioctls, except for two special cases: + * - FE_GET_EVENT is part of the tuning logic on a DVB application; + * - FE_DISEQC_RECV_SLAVE_REPLY is part of DiSEqC 2.0 + * setup + * So, those two ioctls should also return -EPERM, as otherwise + * reading from them would interfere with a DVB tune application + */ + if ((file->f_flags & O_ACCMODE) == O_RDONLY + && (_IOC_DIR(cmd) != _IOC_READ + || cmd == FE_GET_EVENT + || cmd == FE_DISEQC_RECV_SLAVE_REPLY)) { up(&fepriv->sem); return -EPERM; } -- 2.25.1
