kbuild: enable some -Wextra warnings by default

[PATCH 05/12] firmware: dmi-id: add a release callback function

Posted by Arnd Bergmann 1 year, 10 months ago

From: Arnd Bergmann <arnd@arndb.de>

dmi_class uses kfree() as the .release function, but that now causes
a warning with clang-16 as it violates control flow integrity (KCFI)
rules:

drivers/firmware/dmi-id.c:174:17: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
  174 |         .dev_release = (void(*)(struct device *)) kfree,

Add an explicit function to call kfree() instead.

Fixes: 4f5c791a850e ("DMI-based module autoloading")
Link: https://lore.kernel.org/lkml/20240213100238.456912-1-arnd@kernel.org/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
I sent this before but got no comments for it
---
 drivers/firmware/dmi-id.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/dmi-id.c b/drivers/firmware/dmi-id.c
index 5f3a3e913d28..d19c78a78ae3 100644
--- a/drivers/firmware/dmi-id.c
+++ b/drivers/firmware/dmi-id.c
@@ -169,9 +169,14 @@ static int dmi_dev_uevent(const struct device *dev, struct kobj_uevent_env *env)
 	return 0;
 }
 
+static void dmi_dev_release(struct device *dev)
+{
+	kfree(dev);
+}
+
 static struct class dmi_class = {
 	.name = "dmi",
-	.dev_release = (void(*)(struct device *)) kfree,
+	.dev_release = dmi_dev_release,
 	.dev_uevent = dmi_dev_uevent,
 };
 
-- 
2.39.2

Re: [PATCH 05/12] firmware: dmi-id: add a release callback function

Posted by Jean Delvare 1 year, 10 months ago

Hi Arnd,

On Tue, 26 Mar 2024 15:51:30 +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> dmi_class uses kfree() as the .release function, but that now causes
> a warning with clang-16 as it violates control flow integrity (KCFI)
> rules:
> 
> drivers/firmware/dmi-id.c:174:17: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
>   174 |         .dev_release = (void(*)(struct device *)) kfree,
> 
> Add an explicit function to call kfree() instead.
> 
> Fixes: 4f5c791a850e ("DMI-based module autoloading")

Not sure if this fixes tag is really warranted. As I understand it,
your change only removes a warning but there was no actual bug, right?

> Link: https://lore.kernel.org/lkml/20240213100238.456912-1-arnd@kernel.org/
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> I sent this before but got no comments for it

I indeed overlooked your initial submission, my bad.

> ---
>  drivers/firmware/dmi-id.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/dmi-id.c b/drivers/firmware/dmi-id.c
> index 5f3a3e913d28..d19c78a78ae3 100644
> --- a/drivers/firmware/dmi-id.c
> +++ b/drivers/firmware/dmi-id.c
> @@ -169,9 +169,14 @@ static int dmi_dev_uevent(const struct device *dev, struct kobj_uevent_env *env)
>  	return 0;
>  }
>  
> +static void dmi_dev_release(struct device *dev)
> +{
> +	kfree(dev);
> +}
> +
>  static struct class dmi_class = {
>  	.name = "dmi",
> -	.dev_release = (void(*)(struct device *)) kfree,
> +	.dev_release = dmi_dev_release,
>  	.dev_uevent = dmi_dev_uevent,
>  };
>  

Looks good to me, thanks for doing that.

Signed-off-by: Jean Delvare <jdelvare@suse.de>

Will you get this upstream, or do you expect me to take it in my
dmi/for-next branch?

-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH 05/12] firmware: dmi-id: add a release callback function

Posted by Arnd Bergmann 1 year, 10 months ago

On Fri, Mar 29, 2024, at 13:49, Jean Delvare wrote:
> On Tue, 26 Mar 2024 15:51:30 +0100, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@arndb.de>
>> 
>> dmi_class uses kfree() as the .release function, but that now causes
>> a warning with clang-16 as it violates control flow integrity (KCFI)
>> rules:
>> 
>> drivers/firmware/dmi-id.c:174:17: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
>>   174 |         .dev_release = (void(*)(struct device *)) kfree,
>> 
>> Add an explicit function to call kfree() instead.
>> 
>> Fixes: 4f5c791a850e ("DMI-based module autoloading")
>
> Not sure if this fixes tag is really warranted. As I understand it,
> your change only removes a warning but there was no actual bug, right?

As Nathan already commented, it's a real bug. I also add 'Fixes'
tags for false-positives just to document what introduced a
warning. The Fixes tag doesn't automatically mean something gets
backported, though the stable maintainers often end up backporting
warning fixes as well, and it helps identify which kernels
need it.

> Looks good to me, thanks for doing that.
>
> Signed-off-by: Jean Delvare <jdelvare@suse.de>
>
> Will you get this upstream, or do you expect me to take it in my
> dmi/for-next branch?

It would help me if you can apply it to your tree directly.

     Arnd

Re: [PATCH 05/12] firmware: dmi-id: add a release callback function

Posted by Jean Delvare 1 year, 10 months ago

Hi Arnd,

On Thu, 04 Apr 2024 16:07:55 +0200, Arnd Bergmann wrote:
> On Fri, Mar 29, 2024, at 13:49, Jean Delvare wrote:
> > Will you get this upstream, or do you expect me to take it in my
> > dmi/for-next branch?  
> 
> It would help me if you can apply it to your tree directly.

OK, it's in my dmi-for-next branch now:

https://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging.git/log/?h=dmi-for-next

Thanks,
-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH 05/12] firmware: dmi-id: add a release callback function

Posted by Arnd Bergmann 1 year, 10 months ago

On Mon, Apr 8, 2024, at 09:59, Jean Delvare wrote:
> On Thu, 04 Apr 2024 16:07:55 +0200, Arnd Bergmann wrote:
>> On Fri, Mar 29, 2024, at 13:49, Jean Delvare wrote:
>> > Will you get this upstream, or do you expect me to take it in my
>> > dmi/for-next branch?  
>> 
>> It would help me if you can apply it to your tree directly.
>
> OK, it's in my dmi-for-next branch now:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging.git/log/?h=dmi-for-next

Hi Jean,

I see it's in your tree, but I don't see your tree in linux-next.

As all the other fixes from my series got merged, I would like to
merge the patches that turn the warnings on, but that still
causes a build-time regression.

Is there a reason for the dmi-next tree not being part of
linux-next, or should we ask Stephen (added to Cc) to add it?

     Arnd

Re: [PATCH 05/12] firmware: dmi-id: add a release callback function

Posted by Jean Delvare 1 year, 10 months ago

On Fri, 12 Apr 2024 11:42:03 +0200, Arnd Bergmann wrote:
> On Mon, Apr 8, 2024, at 09:59, Jean Delvare wrote:
> > On Thu, 04 Apr 2024 16:07:55 +0200, Arnd Bergmann wrote:  
> >> On Fri, Mar 29, 2024, at 13:49, Jean Delvare wrote:  
> >> > Will you get this upstream, or do you expect me to take it in my
> >> > dmi/for-next branch?    
> >> 
> >> It would help me if you can apply it to your tree directly.  
> >
> > OK, it's in my dmi-for-next branch now:
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging.git/log/?h=dmi-for-next  
> 
> I see it's in your tree, but I don't see your tree in linux-next.
>
> As all the other fixes from my series got merged, I would like to
> merge the patches that turn the warnings on, but that still
> causes a build-time regression.
> 
> Is there a reason for the dmi-next tree not being part of
> linux-next, or should we ask Stephen (added to Cc) to add it?

Hmm, Stephen cleaned up the list of trees he pulls from 2 months ago.
Back then, I objected that I may use my tree again in the future, and I
thought he had added it back to the list, but maybe I misunderstood.

Stephen, can you check if you still pull from tree above, and if not,
add it back to the list? Thanks in advance.

-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH 05/12] firmware: dmi-id: add a release callback function

Posted by Stephen Rothwell 1 year, 9 months ago

Hi Jean,

On Sat, 13 Apr 2024 22:38:57 +0200 Jean Delvare <jdelvare@suse.de> wrote:
>
> Hmm, Stephen cleaned up the list of trees he pulls from 2 months ago.
> Back then, I objected that I may use my tree again in the future, and I
> thought he had added it back to the list, but maybe I misunderstood.
> 
> Stephen, can you check if you still pull from tree above, and if not,
> add it back to the list? Thanks in advance.

I also misunderstood your position at the time.  I have now restored
the dmi tree to linux-next.

-- 
Cheers,
Stephen Rothwell

Re: [PATCH 05/12] firmware: dmi-id: add a release callback function

Posted by Nathan Chancellor 1 year, 10 months ago

On Fri, Mar 29, 2024 at 01:49:17PM +0100, Jean Delvare wrote:
> Hi Arnd,
> 
> On Tue, 26 Mar 2024 15:51:30 +0100, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> > 
> > dmi_class uses kfree() as the .release function, but that now causes
> > a warning with clang-16 as it violates control flow integrity (KCFI)
> > rules:
> > 
> > drivers/firmware/dmi-id.c:174:17: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
> >   174 |         .dev_release = (void(*)(struct device *)) kfree,
> > 
> > Add an explicit function to call kfree() instead.
> > 
> > Fixes: 4f5c791a850e ("DMI-based module autoloading")
> 
> Not sure if this fixes tag is really warranted. As I understand it,
> your change only removes a warning but there was no actual bug, right?

Sort of, the warning is really pointing out that calling this callback
will result in a crash at runtime when the kernel is built with kCFI
enabled, which I would consider a bug.

Cheers,
Nathan