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FLEX_ARRAY_INIT(element_size, total_nr_elements) cannot determine if either parameter is valid, so flex arrays which are statically allocated with this interface can easily become corrupted or reference beyond its allocated memory. This removes FLEX_ARRAY_INIT() as a struct flex_array initializer since no initializer may perform the required checking. Instead, the array is now defined with a new interface: DEFINE_FLEX_ARRAY(name, element_size, total_nr_elements) This may be prefixed with `static' for file scope. This interface includes compile-time checking of the parameters to ensure they are valid. Since the validity of both element_size and total_nr_elements depend on FLEX_ARRAY_BASE_SIZE and FLEX_ARRAY_PART_SIZE, the kernel build will fail if either of these predefined values changes such that the array parameters are no longer valid. Since BUILD_BUG_ON() requires compile time constants, several of the static inline functions that were once local to lib/flex_array.c had to be moved to include/linux/flex_array.h. Signed-off-by: David Rientjes <rientjes@google.com> Acked-by: Dave Hansen <dave@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
73 lines
2.2 KiB
C
73 lines
2.2 KiB
C
#ifndef _FLEX_ARRAY_H
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#define _FLEX_ARRAY_H
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#include <linux/types.h>
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#include <asm/page.h>
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#define FLEX_ARRAY_PART_SIZE PAGE_SIZE
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#define FLEX_ARRAY_BASE_SIZE PAGE_SIZE
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struct flex_array_part;
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/*
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* This is meant to replace cases where an array-like
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* structure has gotten too big to fit into kmalloc()
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* and the developer is getting tempted to use
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* vmalloc().
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*/
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struct flex_array {
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union {
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struct {
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int element_size;
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int total_nr_elements;
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struct flex_array_part *parts[];
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};
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/*
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* This little trick makes sure that
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* sizeof(flex_array) == PAGE_SIZE
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*/
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char padding[FLEX_ARRAY_BASE_SIZE];
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};
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};
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/* Number of bytes left in base struct flex_array, excluding metadata */
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#define FLEX_ARRAY_BASE_BYTES_LEFT \
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(FLEX_ARRAY_BASE_SIZE - offsetof(struct flex_array, parts))
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/* Number of pointers in base to struct flex_array_part pages */
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#define FLEX_ARRAY_NR_BASE_PTRS \
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(FLEX_ARRAY_BASE_BYTES_LEFT / sizeof(struct flex_array_part *))
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/* Number of elements of size that fit in struct flex_array_part */
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#define FLEX_ARRAY_ELEMENTS_PER_PART(size) \
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(FLEX_ARRAY_PART_SIZE / size)
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/*
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* Defines a statically allocated flex array and ensures its parameters are
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* valid.
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*/
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#define DEFINE_FLEX_ARRAY(__arrayname, __element_size, __total) \
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struct flex_array __arrayname = { { { \
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.element_size = (__element_size), \
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.total_nr_elements = (__total), \
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} } }; \
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static inline void __arrayname##_invalid_parameter(void) \
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{ \
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BUILD_BUG_ON((__total) > FLEX_ARRAY_NR_BASE_PTRS * \
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FLEX_ARRAY_ELEMENTS_PER_PART(__element_size)); \
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}
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struct flex_array *flex_array_alloc(int element_size, unsigned int total,
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gfp_t flags);
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int flex_array_prealloc(struct flex_array *fa, unsigned int start,
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unsigned int end, gfp_t flags);
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void flex_array_free(struct flex_array *fa);
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void flex_array_free_parts(struct flex_array *fa);
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int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
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gfp_t flags);
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int flex_array_clear(struct flex_array *fa, unsigned int element_nr);
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void *flex_array_get(struct flex_array *fa, unsigned int element_nr);
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int flex_array_shrink(struct flex_array *fa);
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#endif /* _FLEX_ARRAY_H */
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