[PATCH] staging: most: video: fix registration of an empty comp core_component

[PATCH] staging: most: video: fix registration of an empty comp core_component

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

Currently we have structrues comp (which is empty) and comp_info being
used to register and deregister the component.  This mismatch in naming
occurred from a previous commit that renamed aim_info to comp. Fix this
to use consistent component naming in line with most/net, most/sound etc.

This fixes the message two issues, one with a null empty name when
loading the module:

[ 1485.269515] most_core: registered new core component (null)

and an Oops when removing the module:

[ 1485.277971] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
[ 1485.278648] PGD 0 P4D 0
[ 1485.279253] Oops: 0002 [#2] SMP PTI
[ 1485.279847] CPU: 1 PID: 32629 Comm: modprobe Tainted: P      D WC OE     4.18.0-8-generic #9
[ 1485.280442] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
[ 1485.281040] RIP: 0010:most_deregister_component+0x3c/0x70 [most_core]
.. etc

Fixes: 1b10a0316e2d ("staging: most: video: remove aim designators")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/staging/most/video/video.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/most/video/video.c b/drivers/staging/most/video/video.c
index cf342eb58e10..ad7e28ab9a4f 100644
--- a/drivers/staging/most/video/video.c
+++ b/drivers/staging/most/video/video.c
@@ -530,7 +530,7 @@ static int comp_disconnect_channel(struct most_interface *iface,
 	return 0;
 }
 
-static struct core_component comp_info = {
+static struct core_component comp = {
 	.name = "video",
 	.probe_channel = comp_probe_channel,
 	.disconnect_channel = comp_disconnect_channel,
@@ -565,7 +565,7 @@ static void __exit comp_exit(void)
 	}
 	spin_unlock_irq(&list_lock);
 
-	most_deregister_component(&comp_info);
+	most_deregister_component(&comp);
 	BUG_ON(!list_empty(&video_devices));
 }
 
-- 
2.17.1

Re: [PATCH] staging: most: video: fix registration of an empty comp core_component

[Alexander Stein]

On Wednesday, September 5, 2018, 11:46:05 AM CEST Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Currently we have structrues comp (which is empty) and comp_info being
> used to register and deregister the component.  This mismatch in naming
> occurred from a previous commit that renamed aim_info to comp. Fix this
> to use consistent component naming in line with most/net, most/sound etc.
> 
> This fixes the message two issues, one with a null empty name when
> loading the module:
> 
> [ 1485.269515] most_core: registered new core component (null)
> 
> and an Oops when removing the module:
> 
> [ 1485.277971] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
> [ 1485.278648] PGD 0 P4D 0
> [ 1485.279253] Oops: 0002 [#2] SMP PTI
> [ 1485.279847] CPU: 1 PID: 32629 Comm: modprobe Tainted: P      D WC OE     4.18.0-8-generic #9
> [ 1485.280442] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> [ 1485.281040] RIP: 0010:most_deregister_component+0x3c/0x70 [most_core]
> .. etc
> 
> Fixes: 1b10a0316e2d ("staging: most: video: remove aim designators")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/staging/most/video/video.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/most/video/video.c b/drivers/staging/most/video/video.c
> index cf342eb58e10..ad7e28ab9a4f 100644
> --- a/drivers/staging/most/video/video.c
> +++ b/drivers/staging/most/video/video.c
> @@ -530,7 +530,7 @@ static int comp_disconnect_channel(struct most_interface *iface,
>  	return 0;
>  }
>  
> -static struct core_component comp_info = {
> +static struct core_component comp = {
>  	.name = "video",
>  	.probe_channel = comp_probe_channel,
>  	.disconnect_channel = comp_disconnect_channel,

Doesn't it make more sense to move that variable defintion where currently the forward declaration is?
This way you can't have 2 variables accidentally. You will need forward declarations for those two functions, but a mismatch here results in a linker error rather than a runtime NULL pointer access

Best regards,
Alexander

Re: [PATCH] staging: most: video: fix registration of an empty comp core_component

[Colin Ian King]

On 05/09/18 11:06, Alexander Stein wrote:
> On Wednesday, September 5, 2018, 11:46:05 AM CEST Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> Currently we have structrues comp (which is empty) and comp_info being
>> used to register and deregister the component.  This mismatch in naming
>> occurred from a previous commit that renamed aim_info to comp. Fix this
>> to use consistent component naming in line with most/net, most/sound etc.
>>
>> This fixes the message two issues, one with a null empty name when
>> loading the module:
>>
>> [ 1485.269515] most_core: registered new core component (null)
>>
>> and an Oops when removing the module:
>>
>> [ 1485.277971] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
>> [ 1485.278648] PGD 0 P4D 0
>> [ 1485.279253] Oops: 0002 [#2] SMP PTI
>> [ 1485.279847] CPU: 1 PID: 32629 Comm: modprobe Tainted: P      D WC OE     4.18.0-8-generic #9
>> [ 1485.280442] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
>> [ 1485.281040] RIP: 0010:most_deregister_component+0x3c/0x70 [most_core]
>> .. etc
>>
>> Fixes: 1b10a0316e2d ("staging: most: video: remove aim designators")
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>> ---
>>  drivers/staging/most/video/video.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/most/video/video.c b/drivers/staging/most/video/video.c
>> index cf342eb58e10..ad7e28ab9a4f 100644
>> --- a/drivers/staging/most/video/video.c
>> +++ b/drivers/staging/most/video/video.c
>> @@ -530,7 +530,7 @@ static int comp_disconnect_channel(struct most_interface *iface,
>>  	return 0;
>>  }
>>  
>> -static struct core_component comp_info = {
>> +static struct core_component comp = {
>>  	.name = "video",
>>  	.probe_channel = comp_probe_channel,
>>  	.disconnect_channel = comp_disconnect_channel,
> 
> Doesn't it make more sense to move that variable defintion where currently the forward declaration is?

Probably, I was just keeping this the same as the other most/* drivers
to be consistent with those for now while just fixing this current buglet.

> This way you can't have 2 variables accidentally. You will need forward declarations for those two functions, but a mismatch here results in a linker error rather than a runtime NULL pointer access
> 
> Best regards,
> Alexander
> 
> 
>