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

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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: 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>
This commit is contained in:
Greg Kroah-Hartman 2022-12-05 13:12:03 +01:00
parent 50dc8d18f6
commit 64f6a5d192
1 changed files with 13 additions and 0 deletions
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13
include/linux/container_of.h
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@ -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 */