Two readonly ioctls can't be allowed if the frontend device
is opened in read only mode. Explain why.
Signed-off-by: Mauro Carvalho Chehab <mche...@s-opensource.com>
---
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 01bd19fd4c57..7dda5acea3f2 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -1940,9 +1940,23 @@ 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 at 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;
}
--
2.13.5
