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overflow.h: Add allocation size calculation helpers

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In preparation for replacing unchecked overflows for memory allocations,
this creates helpers for the 3 most common calculations:

array_size(a, b): 2-dimensional array
array3_size(a, b, c): 3-dimensional array
struct_size(ptr, member, n): struct followed by n-many trailing members

Each of these return SIZE_MAX on overflow instead of wrapping around.

(Additionally renames a variable named "array_size" to avoid future
collision.)

Co-developed-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2018-05-07 16:47:02 -07:00
parent 8fee81aa45
commit 610b15c50e
2 changed files with 78 additions and 5 deletions
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10
drivers/md/dm-table.c
View File

@ -548,14 +548,14 @@ static int adjoin(struct dm_table *table, struct dm_target *ti)
* On the other hand, dm-switch needs to process bulk data using messages and
* excessive use of GFP_NOIO could cause trouble.
*/
static char **realloc_argv(unsigned *array_size, char **old_argv)
static char **realloc_argv(unsigned *size, char **old_argv)
{
char **argv;
unsigned new_size;
gfp_t gfp;
if (*array_size) {
new_size = *array_size * 2;
if (*size) {
new_size = *size * 2;
gfp = GFP_KERNEL;
} else {
new_size = 8;
@ -563,8 +563,8 @@ static char **realloc_argv(unsigned *array_size, char **old_argv)
}
argv = kmalloc(new_size * sizeof(*argv), gfp);
if (argv) {
memcpy(argv, old_argv, *array_size * sizeof(*argv));
*array_size = new_size;
memcpy(argv, old_argv, *size * sizeof(*argv));
*size = new_size;
}
kfree(old_argv);

73
include/linux/overflow.h
View File

@ -202,4 +202,77 @@
#endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */
/**
* array_size() - Calculate size of 2-dimensional array.
*
* @a: dimension one
* @b: dimension two
*
* Calculates size of 2-dimensional array: @a * @b.
*
* Returns: number of bytes needed to represent the array or SIZE_MAX on
* overflow.
*/
static inline __must_check size_t array_size(size_t a, size_t b)
{
size_t bytes;
if (check_mul_overflow(a, b, &bytes))
return SIZE_MAX;
return bytes;
}
/**
* array3_size() - Calculate size of 3-dimensional array.
*
* @a: dimension one
* @b: dimension two
* @c: dimension three
*
* Calculates size of 3-dimensional array: @a * @b * @c.
*
* Returns: number of bytes needed to represent the array or SIZE_MAX on
* overflow.
*/
static inline __must_check size_t array3_size(size_t a, size_t b, size_t c)
{
size_t bytes;
if (check_mul_overflow(a, b, &bytes))
return SIZE_MAX;
if (check_mul_overflow(bytes, c, &bytes))
return SIZE_MAX;
return bytes;
}
static inline __must_check size_t __ab_c_size(size_t n, size_t size, size_t c)
{
size_t bytes;
if (check_mul_overflow(n, size, &bytes))
return SIZE_MAX;
if (check_add_overflow(bytes, c, &bytes))
return SIZE_MAX;
return bytes;
}
/**
* struct_size() - Calculate size of structure with trailing array.
* @p: Pointer to the structure.
* @member: Name of the array member.
* @n: Number of elements in the array.
*
* Calculates size of memory needed for structure @p followed by an
* array of @n @member elements.
*
* Return: number of bytes needed or SIZE_MAX on overflow.
*/
#define struct_size(p, member, n) \
__ab_c_size(n, \
sizeof(*(p)->member) + __must_be_array((p)->member),\
sizeof(*(p)))
#endif /* __LINUX_OVERFLOW_H */