Ack: [SRU Oneiric/Precise][Quantal][PATCH] [media] Avoid sysfs oops when an rc_dev's raw device is absent

[Leann Ogasawara]

Applied to Quantal master-next.

Ack for Oneiric and Precise SRU:

Acked-by: Leann Ogasawara <leann.ogasawara at canonical.com>

I assume you'll submit to upstream stable as well?

Thanks,
Leann

On 08/06/2012 10:06 AM, Herton Ronaldo Krzesinski wrote:
> From: Douglas Bagnall <douglas at paradise.net.nz>
>
> For some reason, when the lirc daemon learns that a usb remote control
> has been unplugged, it wants to read the sysfs attributes of the
> disappearing device. This is useful for uncovering transient
> inconsistencies, but less so for keeping the system running when such
> inconsistencies exist.
>
> Under some circumstances (like every time I unplug my dvb stick from
> my laptop), lirc catches an rc_dev whose raw event handler has been
> removed (presumably by ir_raw_event_unregister), and proceeds to
> interrogate the raw protocols supported by the NULL pointer.
>
> This patch avoids the NULL dereference, and ignores the issue of how
> this state of affairs came about in the first place.
>
> Version 2 incorporates changes recommended by Mauro Carvalho Chehab
> (-ENODEV instead of -EINVAL, and a signed-off-by).
>
> Signed-off-by: Douglas Bagnall <douglas at paradise.net.nz>
> Signed-off-by: Mauro Carvalho Chehab <mchehab at redhat.com>
> (cherry picked from commit 720bb6436ff30fccad05cf5bdf961ea5b1f5686d upstream)
> BugLink: http://bugs.launchpad.net/bugs/1015836
> Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
> ---
>  drivers/media/rc/rc-main.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> Bug was reported against Precise, but looking at the code Oneiric seems
> affected as well. Natty would be affected too, but seems its code have
> more problems (for example, it misses commit 08aeb7c "rc: add locking to fix
> register/show race"), and I'm not sure it's worth touching Natty at this
> stage.
>
> I did a quick verification against one of the oopses on the bug also, the
> patch looks good (code patched will address crash matched with symbols from
> linux-image-3.2.0-26-generic-dbgsym_3.2.0-26.41_amd64.ddeb). And seems a fix
> that is worth for stable upstream too, I'll send it there as well.
>
> diff --git a/drivers/media/rc/rc-main.c b/drivers/media/rc/rc-main.c
> index 6e16b09..cabc19c 100644
> --- a/drivers/media/rc/rc-main.c
> +++ b/drivers/media/rc/rc-main.c
> @@ -775,10 +775,11 @@ static ssize_t show_protocols(struct device *device,
>  	if (dev->driver_type == RC_DRIVER_SCANCODE) {
>  		enabled = dev->rc_map.rc_type;
>  		allowed = dev->allowed_protos;
> -	} else {
> +	} else if (dev->raw) {
>  		enabled = dev->raw->enabled_protocols;
>  		allowed = ir_raw_get_allowed_protocols();
> -	}
> +	} else
> +		return -ENODEV;
>  
>  	IR_dprintk(1, "allowed - 0x%llx, enabled - 0x%llx\n",
>  		   (long long)allowed,