* [PATCH] container_of: add type safety
@ 2023-03-08 17:35 Michael S. Tsirkin
2023-03-08 17:57 ` Greg Kroah-Hartman
2023-03-08 17:57 ` Greg Kroah-Hartman
0 siblings, 2 replies; 4+ messages in thread
From: Michael S. Tsirkin @ 2023-03-08 17:35 UTC (permalink / raw)
To: linux-kernel
Cc: Jason Gunthorpe, Sakari Ailus, Matthew Wilcox, Jason Gunthorpe,
Andy Shevchenko, Rafael J . Wysocki, Greg Kroah-Hartman
Using a wrong member in container_of will result in an error.
No so for container_of_const - it is just a cast so will
happily give you a wrong pointer.
Use logic from container_of to add safety.
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20221205121206.166576-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/container_of.h | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/include/linux/container_of.h b/include/linux/container_of.h
index 1d898f9158b4..5d87faf72e0a 100644
--- a/include/linux/container_of.h
+++ b/include/linux/container_of.h
@@ -29,10 +29,13 @@
* @type: the type of the container struct this is embedded in.
* @member: the name of the member within the struct.
*/
-#define container_of_const(ptr, type, member) \
+#define container_of_const(ptr, type, member) ({ \
+ static_assert(__same_type(*(ptr), ((type *)0)->member) || \
+ __same_type(*(ptr), void), \
+ "pointer type mismatch in container_of()"); \
_Generic(ptr, \
const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\
default: ((type *)container_of(ptr, type, member)) \
- )
+ ); })
#endif /* _LINUX_CONTAINER_OF_H */
--
MST
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] container_of: add type safety
2023-03-08 17:35 [PATCH] container_of: add type safety Michael S. Tsirkin
@ 2023-03-08 17:57 ` Greg Kroah-Hartman
2023-03-08 20:58 ` Michael S. Tsirkin
2023-03-08 17:57 ` Greg Kroah-Hartman
1 sibling, 1 reply; 4+ messages in thread
From: Greg Kroah-Hartman @ 2023-03-08 17:57 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: linux-kernel, Jason Gunthorpe, Sakari Ailus, Matthew Wilcox,
Jason Gunthorpe, Andy Shevchenko, Rafael J . Wysocki
On Wed, Mar 08, 2023 at 12:35:03PM -0500, Michael S. Tsirkin wrote:
> Using a wrong member in container_of will result in an error.
> No so for container_of_const - it is just a cast so will
> happily give you a wrong pointer.
>
> Use logic from container_of to add safety.
>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> Cc: Jason Gunthorpe <jgg@nvidia.com>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
> Cc: Rafael J. Wysocki <rafael@kernel.org>
> Link: https://lore.kernel.org/r/20221205121206.166576-1-gregkh@linuxfoundation.org
That's the wrong link, that's not this patch, that was an old patch.
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
I did not sign off on this. NEVER do that, you just made a legal
statement in my name, why?
Why did you not sign off on it?
totally confused...
> ---
> include/linux/container_of.h | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/container_of.h b/include/linux/container_of.h
> index 1d898f9158b4..5d87faf72e0a 100644
> --- a/include/linux/container_of.h
> +++ b/include/linux/container_of.h
> @@ -29,10 +29,13 @@
> * @type: the type of the container struct this is embedded in.
> * @member: the name of the member within the struct.
> */
> -#define container_of_const(ptr, type, member) \
> +#define container_of_const(ptr, type, member) ({ \
> + static_assert(__same_type(*(ptr), ((type *)0)->member) || \
> + __same_type(*(ptr), void), \
> + "pointer type mismatch in container_of()"); \
Why is this needed because:
> _Generic(ptr, \
> const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\
> default: ((type *)container_of(ptr, type, member)) \
container_of() is used here, so shouldn't the assert trigger there if
you get things wrong?
So why is this change needed at all?
thanks,
greg k-h
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] container_of: add type safety
2023-03-08 17:35 [PATCH] container_of: add type safety Michael S. Tsirkin
2023-03-08 17:57 ` Greg Kroah-Hartman
@ 2023-03-08 17:57 ` Greg Kroah-Hartman
1 sibling, 0 replies; 4+ messages in thread
From: Greg Kroah-Hartman @ 2023-03-08 17:57 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: linux-kernel, Jason Gunthorpe, Sakari Ailus, Matthew Wilcox,
Jason Gunthorpe, Andy Shevchenko, Rafael J . Wysocki
On Wed, Mar 08, 2023 at 12:35:03PM -0500, Michael S. Tsirkin wrote:
> Using a wrong member in container_of will result in an error.
> No so for container_of_const - it is just a cast so will
> happily give you a wrong pointer.
>
> Use logic from container_of to add safety.
Also your subject line is wrong :(
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] container_of: add type safety
2023-03-08 17:57 ` Greg Kroah-Hartman
@ 2023-03-08 20:58 ` Michael S. Tsirkin
0 siblings, 0 replies; 4+ messages in thread
From: Michael S. Tsirkin @ 2023-03-08 20:58 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: linux-kernel, Jason Gunthorpe, Sakari Ailus, Matthew Wilcox,
Jason Gunthorpe, Andy Shevchenko, Rafael J . Wysocki
On Wed, Mar 08, 2023 at 06:57:13PM +0100, Greg Kroah-Hartman wrote:
> On Wed, Mar 08, 2023 at 12:35:03PM -0500, Michael S. Tsirkin wrote:
> > Using a wrong member in container_of will result in an error.
> > No so for container_of_const - it is just a cast so will
> > happily give you a wrong pointer.
> >
> > Use logic from container_of to add safety.
> >
> > Cc: Jason Gunthorpe <jgg@ziepe.ca>
> > Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
> > Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> > Cc: Jason Gunthorpe <jgg@nvidia.com>
> > Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
> > Cc: Rafael J. Wysocki <rafael@kernel.org>
> > Link: https://lore.kernel.org/r/20221205121206.166576-1-gregkh@linuxfoundation.org
>
> That's the wrong link, that's not this patch, that was an old patch.
>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> I did not sign off on this. NEVER do that, you just made a legal
> statement in my name, why?
>
> Why did you not sign off on it?
>
> totally confused...
Ooops. I started with people who signed off on the original one
and replaced S.O.B with a CC. Forgot to replace it for yours
and then the script checking patches saw a signoff and was happy
so I didn't notice I forgot to sign it myself ...
However ...
> > ---
> > include/linux/container_of.h | 7 +++++--
> > 1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/container_of.h b/include/linux/container_of.h
> > index 1d898f9158b4..5d87faf72e0a 100644
> > --- a/include/linux/container_of.h
> > +++ b/include/linux/container_of.h
> > @@ -29,10 +29,13 @@
> > * @type: the type of the container struct this is embedded in.
> > * @member: the name of the member within the struct.
> > */
> > -#define container_of_const(ptr, type, member) \
> > +#define container_of_const(ptr, type, member) ({ \
> > + static_assert(__same_type(*(ptr), ((type *)0)->member) || \
> > + __same_type(*(ptr), void), \
> > + "pointer type mismatch in container_of()"); \
>
> Why is this needed because:
>
>
> > _Generic(ptr, \
> > const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\
> > default: ((type *)container_of(ptr, type, member)) \
>
> container_of() is used here, so shouldn't the assert trigger there if
> you get things wrong?
>
> So why is this change needed at all?
>
> thanks,
>
> greg k-h
Hmm. I think I was confused. Error did not seem to trigger but
I tried again and it does. Ignore this please.
Sorry about the noise.
--
MST
^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-03-08 17:35 [PATCH] container_of: add type safety Michael S. Tsirkin
2023-03-08 17:57 ` Greg Kroah-Hartman
2023-03-08 20:58 ` Michael S. Tsirkin
2023-03-08 17:57 ` Greg Kroah-Hartman
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