Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH v2 1/4] container_of: add container_of_const() that preserves const-ness of the pointer | Date | Mon, 5 Dec 2022 13:12:03 +0100 |
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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: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- v2: - removed one parameter, now matches container_of(), thanks to suggestion from Sakari - changed Jason's tag to suggested-by and reviewed-by - added Andy's tag
include/linux/container_of.h | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/include/linux/container_of.h b/include/linux/container_of.h index 2008e9f4058c..1d898f9158b4 100644 --- a/include/linux/container_of.h +++ b/include/linux/container_of.h @@ -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 */ -- 2.38.1
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