Commit 64f6a5d1 authored Dec 05, 2022 by Greg Kroah-Hartman

container_of: add container_of_const() that preserves const-ness of the pointer



container_of does not preserve the const-ness of a pointer that is
passed into it, which can cause C code that passes in a const pointer to
get a pointer back that is not const and then scribble all over the data
in it.  To prevent this, container_of_const() will preserve the const
status of the pointer passed into it using the newly available _Generic()
method.

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: 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>

parent 50dc8d18

include/linux/container_of.h

+13 −0

Original line number	Diff line number	Diff line
		@@ -22,4 +22,17 @@
		"pointer type mismatch in container_of()"); \
		((type *)(__mptr - offsetof(type, member))); })

		/**
		* container_of_const - cast a member of a structure out to the containing
		* structure and preserve the const-ness of the pointer
		* @ptr: the pointer to the member
		* @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) \
		_Generic(ptr, \
		const typeof((ptr)) : ((const type *)container_of(ptr, type, member)),\
		default: ((type *)container_of(ptr, type, member)) \
		)

		#endif /* _LINUX_CONTAINER_OF_H */