From 55089d34f18cfbbcfcb5279b041c1b545ca8e657 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Fri, 5 Jun 2020 09:25:11 -0700 Subject: [PATCH] media: dvb_frontend: fix return values for FE_SET_PROPERTY commit 259a41d9ae8f3689742267f340ad2b159d00b302 upstream There are several problems with regards to the return of FE_SET_PROPERTY. The original idea were to return per-property return codes via tvp->result field, and to return an updated set of values. However, that never worked. What's actually implemented is: - the FE_SET_PROPERTY implementation doesn't call .get_frontend callback in order to get the actual parameters after return; - the tvp->result field is only filled if there's no error. So, it is always filled with zero; - FE_SET_PROPERTY doesn't call memdup_user() nor any other copy_to_user() function. So, any changes to the properties will be lost; - FE_SET_PROPERTY is declared as a write-only ioctl (IOW). While we could fix the above, it could cause regressions. So, let's just assume what the code really does, updating the documentation accordingly and removing the logic that would update the discarded tvp->result. Reviewed-by: Shuah Khan Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Florian Fainelli Signed-off-by: Greg Kroah-Hartman --- Documentation/media/uapi/dvb/fe-get-property.rst | 7 +++++-- drivers/media/dvb-core/dvb_frontend.c | 2 -- include/uapi/linux/dvb/frontend.h | 2 +- 3 files changed, 6 insertions(+), 5 deletions(-) diff --git a/Documentation/media/uapi/dvb/fe-get-property.rst b/Documentation/media/uapi/dvb/fe-get-property.rst index 015d4db..c80c5fc 100644 --- a/Documentation/media/uapi/dvb/fe-get-property.rst +++ b/Documentation/media/uapi/dvb/fe-get-property.rst @@ -48,8 +48,11 @@ depends on the delivery system and on the device: - This call requires read/write access to the device. - - At return, the values are updated to reflect the actual parameters - used. +.. note:: + + At return, the values aren't updated to reflect the actual + parameters used. If the actual parameters are needed, an explicit + call to ``FE_GET_PROPERTY`` is needed. - ``FE_GET_PROPERTY:`` diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c index 673cefb..ca4959b 100644 --- a/drivers/media/dvb-core/dvb_frontend.c +++ b/drivers/media/dvb-core/dvb_frontend.c @@ -2127,7 +2127,6 @@ static int dvb_frontend_handle_ioctl(struct file *file, kfree(tvp); return err; } - (tvp + i)->result = err; } kfree(tvp); break; @@ -2172,7 +2171,6 @@ static int dvb_frontend_handle_ioctl(struct file *file, kfree(tvp); return err; } - (tvp + i)->result = err; } if (copy_to_user((void __user *)tvps->props, tvp, diff --git a/include/uapi/linux/dvb/frontend.h b/include/uapi/linux/dvb/frontend.h index 16a318f..b653754 100644 --- a/include/uapi/linux/dvb/frontend.h +++ b/include/uapi/linux/dvb/frontend.h @@ -830,7 +830,7 @@ struct dtv_fe_stats { * @cmd: Digital TV command. * @reserved: Not used. * @u: Union with the values for the command. - * @result: Result of the command set (currently unused). + * @result: Unused * * The @u union may have either one of the values below: * -- 2.7.4