From 45b588d6e5cc172704bac0c998ce54873b149b22 Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Mon, 21 Sep 2009 17:04:33 -0700 Subject: flex_array: introduce DEFINE_FLEX_ARRAY 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the kernel build will fail if either of these predefined values changes such that the array parameters are no longer valid.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 Acked-by: Dave Hansen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/flex_array.h | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) (limited to 'include') diff --git a/include/linux/flex_array.h b/include/linux/flex_array.h index f12401e485f..1d747f72298 100644 --- a/include/linux/flex_array.h +++ b/include/linux/flex_array.h @@ -31,10 +31,32 @@ struct flex_array { }; }; -#define FLEX_ARRAY_INIT(size, total) { { {\ - .element_size = (size), \ - .total_nr_elements = (total), \ -} } } +/* Number of bytes left in base struct flex_array, excluding metadata */ +#define FLEX_ARRAY_BASE_BYTES_LEFT \ + (FLEX_ARRAY_BASE_SIZE - offsetof(struct flex_array, parts)) + +/* Number of pointers in base to struct flex_array_part pages */ +#define FLEX_ARRAY_NR_BASE_PTRS \ + (FLEX_ARRAY_BASE_BYTES_LEFT / sizeof(struct flex_array_part *)) + +/* Number of elements of size that fit in struct flex_array_part */ +#define FLEX_ARRAY_ELEMENTS_PER_PART(size) \ + (FLEX_ARRAY_PART_SIZE / size) + +/* + * Defines a statically allocated flex array and ensures its parameters are + * valid. + */ +#define DEFINE_FLEX_ARRAY(__arrayname, __element_size, __total) \ + struct flex_array __arrayname = { { { \ + .element_size = (__element_size), \ + .total_nr_elements = (__total), \ + } } }; \ + static inline void __arrayname##_invalid_parameter(void) \ + { \ + BUILD_BUG_ON((__total) > FLEX_ARRAY_NR_BASE_PTRS * \ + FLEX_ARRAY_ELEMENTS_PER_PART(__element_size)); \ + } struct flex_array *flex_array_alloc(int element_size, unsigned int total, gfp_t flags); -- cgit v1.2.3-70-g09d2