From: Kees Cook keescook@chromium.org
commit 610b15c50e86eb1e4b77274fabcaea29ac72d6a8 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/md/dm-table.c | 10 +++--- include/linux/overflow.h | 73 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 78 insertions(+), 5 deletions(-)
--- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -516,14 +516,14 @@ static int adjoin(struct dm_table *table * 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; @@ -531,8 +531,8 @@ static char **realloc_argv(unsigned *arr } 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); --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -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 */