[PATCH] container_of: add type safety

Michael S. Tsirkin
2023-03-08T17:36:00Z

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