| Message ID | b28a6f75-eb46-4d71-a919-b4c9c8e35124@xs4all.nl (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | media: mc: mark the media devnode as registered from the, start | expand |
Hi Hans, Thanks for the patch. On Fri, Feb 23, 2024 at 09:46:19AM +0100, Hans Verkuil wrote: > First the media device node was created, and if successful it was > marked as 'registered'. This leaves a small race condition where > an application can open the device node and get an error back > because the 'registered' flag was not yet set. > > Change the order: first set the 'registered' flag, then actually > register the media device node. If that fails, then clear the flag. > > Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> > --- > drivers/media/mc/mc-devnode.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/media/mc/mc-devnode.c b/drivers/media/mc/mc-devnode.c > index 7f67825c8757..318e267e798e 100644 > --- a/drivers/media/mc/mc-devnode.c > +++ b/drivers/media/mc/mc-devnode.c > @@ -245,15 +245,14 @@ int __must_check media_devnode_register(struct media_device *mdev, > kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor); > > /* Part 3: Add the media and char device */ > + set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); > ret = cdev_device_add(&devnode->cdev, &devnode->dev); > if (ret < 0) { > + clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); > pr_err("%s: cdev_device_add failed\n", __func__); > goto cdev_add_error; > } > > - /* Part 4: Activate this minor. The char device can now be used. */ > - set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); > - > return 0; > > cdev_add_error:
Hi Hans, Thank you for the patch. There's a typo in the, commit subject. :-) On Fri, Feb 23, 2024 at 09:46:19AM +0100, Hans Verkuil wrote: > First the media device node was created, and if successful it was > marked as 'registered'. This leaves a small race condition where > an application can open the device node and get an error back > because the 'registered' flag was not yet set. > > Change the order: first set the 'registered' flag, then actually > register the media device node. If that fails, then clear the flag. > > Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> This looks fine for now, so, with the extra comma removed, Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> I however wonder if we couldn't get rid of the flag and delegate the registration test to cdev. > --- > drivers/media/mc/mc-devnode.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/media/mc/mc-devnode.c b/drivers/media/mc/mc-devnode.c > index 7f67825c8757..318e267e798e 100644 > --- a/drivers/media/mc/mc-devnode.c > +++ b/drivers/media/mc/mc-devnode.c > @@ -245,15 +245,14 @@ int __must_check media_devnode_register(struct media_device *mdev, > kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor); > > /* Part 3: Add the media and char device */ > + set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); > ret = cdev_device_add(&devnode->cdev, &devnode->dev); > if (ret < 0) { > + clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); > pr_err("%s: cdev_device_add failed\n", __func__); > goto cdev_add_error; > } > > - /* Part 4: Activate this minor. The char device can now be used. */ > - set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); > - > return 0; > > cdev_add_error:
Hi Laurent, On Fri, Feb 23, 2024 at 12:00:53PM +0200, Laurent Pinchart wrote: > I however wonder if we couldn't get rid of the flag and delegate the > registration test to cdev. I'd see how this could be done after merging the lifetime management patches.
diff --git a/drivers/media/mc/mc-devnode.c b/drivers/media/mc/mc-devnode.c index 7f67825c8757..318e267e798e 100644 --- a/drivers/media/mc/mc-devnode.c +++ b/drivers/media/mc/mc-devnode.c @@ -245,15 +245,14 @@ int __must_check media_devnode_register(struct media_device *mdev, kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor); /* Part 3: Add the media and char device */ + set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); ret = cdev_device_add(&devnode->cdev, &devnode->dev); if (ret < 0) { + clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); pr_err("%s: cdev_device_add failed\n", __func__); goto cdev_add_error; } - /* Part 4: Activate this minor. The char device can now be used. */ - set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); - return 0; cdev_add_error:
First the media device node was created, and if successful it was marked as 'registered'. This leaves a small race condition where an application can open the device node and get an error back because the 'registered' flag was not yet set. Change the order: first set the 'registered' flag, then actually register the media device node. If that fails, then clear the flag. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> --- drivers/media/mc/mc-devnode.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)