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author | Kees Cook <keescook@chromium.org> | 2018-05-07 16:47:02 -0700 |
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committer | Kees Cook <keescook@chromium.org> | 2018-06-05 12:16:51 -0700 |
commit | 610b15c50e86eb1e4b77274fabcaea29ac72d6a8 (patch) | |
tree | d2cc1abd8221f8b83a46331f0a3814b03482d783 /include/linux/overflow.h | |
parent | 8fee81aa4598484c073c845281a25d94fb204cf6 (diff) | |
download | linux-stable-610b15c50e86eb1e4b77274fabcaea29ac72d6a8.tar.gz linux-stable-610b15c50e86eb1e4b77274fabcaea29ac72d6a8.tar.bz2 linux-stable-610b15c50e86eb1e4b77274fabcaea29ac72d6a8.zip |
overflow.h: Add allocation size calculation helpers
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>
Diffstat (limited to 'include/linux/overflow.h')
-rw-r--r-- | include/linux/overflow.h | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/include/linux/overflow.h b/include/linux/overflow.h index c8890ec358a7..8712ff70995f 100644 --- 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 */ |