From: Kees Cook keescook@chromium.org
[ Upstream commit e1be43d9b5d0d1310dbd90185a8e5c7145dde40f ]
In order to perform more open-coded replacements of common allocation size arithmetic, the kernel needs saturating (SIZE_MAX) helpers for multiplication, addition, and subtraction. For example, it is common in allocators, especially on realloc, to add to an existing size:
p = krealloc(map->patch, sizeof(struct reg_sequence) * (map->patch_regs + num_regs), GFP_KERNEL);
There is no existing saturating replacement for this calculation, and just leaving the addition open coded inside array_size() could potentially overflow as well. For example, an overflow in an expression for a size_t argument might wrap to zero:
array_size(anything, something_at_size_max + 1) == 0
Introduce size_mul(), size_add(), and size_sub() helpers that implicitly promote arguments to size_t and saturated calculations for use in allocations. With these helpers it is also possible to redefine array_size(), array3_size(), flex_array_size(), and struct_size() in terms of the new helpers.
As with the check_*_overflow() helpers, the new helpers use __must_check, though what is really desired is a way to make sure that assignment is only to a size_t lvalue. Without this, it's still possible to introduce overflow/underflow via type conversion (i.e. from size_t to int). Enforcing this will currently need to be left to static analysis or future use of -Wconversion.
Additionally update the overflow unit tests to force runtime evaluation for the pathological cases.
Cc: Rasmus Villemoes linux@rasmusvillemoes.dk Cc: Gustavo A. R. Silva gustavoars@kernel.org Cc: Nathan Chancellor nathan@kernel.org Cc: Jason Gunthorpe jgg@ziepe.ca Cc: Nick Desaulniers ndesaulniers@google.com Cc: Leon Romanovsky leon@kernel.org Cc: Keith Busch kbusch@kernel.org Cc: Len Baker len.baker@gmx.com Signed-off-by: Kees Cook keescook@chromium.org Stable-dep-of: e001e6086939 ("fs/ntfs3: Harden against integer overflows") Signed-off-by: Sasha Levin sashal@kernel.org --- Documentation/process/deprecated.rst | 20 ++++- include/linux/overflow.h | 110 +++++++++++++++++---------- lib/test_overflow.c | 98 ++++++++++++++++++++++++ 3 files changed, 184 insertions(+), 44 deletions(-)
diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst index 8ced754a5a0f..f3484f60eae5 100644 --- a/Documentation/process/deprecated.rst +++ b/Documentation/process/deprecated.rst @@ -70,6 +70,9 @@ Instead, the 2-factor form of the allocator should be used::
foo = kmalloc_array(count, size, GFP_KERNEL);
+Specifically, kmalloc() can be replaced with kmalloc_array(), and +kzalloc() can be replaced with kcalloc(). + If no 2-factor form is available, the saturate-on-overflow helpers should be used::
@@ -90,9 +93,20 @@ Instead, use the helper:: array usage and switch to a `flexible array member <#zero-length-and-one-element-arrays>`_ instead.
-See array_size(), array3_size(), and struct_size(), -for more details as well as the related check_add_overflow() and -check_mul_overflow() family of functions. +For other calculations, please compose the use of the size_mul(), +size_add(), and size_sub() helpers. For example, in the case of:: + + foo = krealloc(current_size + chunk_size * (count - 3), GFP_KERNEL); + +Instead, use the helpers:: + + foo = krealloc(size_add(current_size, + size_mul(chunk_size, + size_sub(count, 3))), GFP_KERNEL); + +For more details, also see array3_size() and flex_array_size(), +as well as the related check_mul_overflow(), check_add_overflow(), +check_sub_overflow(), and check_shl_overflow() family of functions.
simple_strtol(), simple_strtoll(), simple_strtoul(), simple_strtoull() ---------------------------------------------------------------------- diff --git a/include/linux/overflow.h b/include/linux/overflow.h index 4669632bd72b..59d7228104d0 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -118,81 +118,94 @@ static inline bool __must_check __must_check_overflow(bool overflow) }))
/** - * array_size() - Calculate size of 2-dimensional array. - * - * @a: dimension one - * @b: dimension two + * size_mul() - Calculate size_t multiplication with saturation at SIZE_MAX * - * Calculates size of 2-dimensional array: @a * @b. + * @factor1: first factor + * @factor2: second factor * - * Returns: number of bytes needed to represent the array or SIZE_MAX on - * overflow. + * Returns: calculate @factor1 * @factor2, both promoted to size_t, + * with any overflow causing the return value to be SIZE_MAX. The + * lvalue must be size_t to avoid implicit type conversion. */ -static inline __must_check size_t array_size(size_t a, size_t b) +static inline size_t __must_check size_mul(size_t factor1, size_t factor2) { size_t bytes;
- if (check_mul_overflow(a, b, &bytes)) + if (check_mul_overflow(factor1, factor2, &bytes)) return SIZE_MAX;
return bytes; }
/** - * array3_size() - Calculate size of 3-dimensional array. + * size_add() - Calculate size_t addition with saturation at SIZE_MAX * - * @a: dimension one - * @b: dimension two - * @c: dimension three - * - * Calculates size of 3-dimensional array: @a * @b * @c. + * @addend1: first addend + * @addend2: second addend * - * Returns: number of bytes needed to represent the array or SIZE_MAX on - * overflow. + * Returns: calculate @addend1 + @addend2, both promoted to size_t, + * with any overflow causing the return value to be SIZE_MAX. The + * lvalue must be size_t to avoid implicit type conversion. */ -static inline __must_check size_t array3_size(size_t a, size_t b, size_t c) +static inline size_t __must_check size_add(size_t addend1, size_t addend2) { size_t bytes;
- if (check_mul_overflow(a, b, &bytes)) - return SIZE_MAX; - if (check_mul_overflow(bytes, c, &bytes)) + if (check_add_overflow(addend1, addend2, &bytes)) return SIZE_MAX;
return bytes; }
-/* - * Compute a*b+c, returning SIZE_MAX on overflow. Internal helper for - * struct_size() below. +/** + * size_sub() - Calculate size_t subtraction with saturation at SIZE_MAX + * + * @minuend: value to subtract from + * @subtrahend: value to subtract from @minuend + * + * Returns: calculate @minuend - @subtrahend, both promoted to size_t, + * with any overflow causing the return value to be SIZE_MAX. For + * composition with the size_add() and size_mul() helpers, neither + * argument may be SIZE_MAX (or the result with be forced to SIZE_MAX). + * The lvalue must be size_t to avoid implicit type conversion. */ -static inline __must_check size_t __ab_c_size(size_t a, size_t b, size_t c) +static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend) { size_t bytes;
- if (check_mul_overflow(a, b, &bytes)) - return SIZE_MAX; - if (check_add_overflow(bytes, c, &bytes)) + if (minuend == SIZE_MAX || subtrahend == SIZE_MAX || + check_sub_overflow(minuend, subtrahend, &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. - * @count: Number of elements in the array. + * array_size() - Calculate size of 2-dimensional array. * - * Calculates size of memory needed for structure @p followed by an - * array of @count number of @member elements. + * @a: dimension one + * @b: dimension two * - * Return: number of bytes needed or SIZE_MAX on overflow. + * Calculates size of 2-dimensional array: @a * @b. + * + * Returns: number of bytes needed to represent the array or SIZE_MAX on + * overflow. */ -#define struct_size(p, member, count) \ - __ab_c_size(count, \ - sizeof(*(p)->member) + __must_be_array((p)->member),\ - sizeof(*(p))) +#define array_size(a, b) size_mul(a, b) + +/** + * 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. + */ +#define array3_size(a, b, c) size_mul(size_mul(a, b), c)
/** * flex_array_size() - Calculate size of a flexible array member @@ -208,7 +221,22 @@ static inline __must_check size_t __ab_c_size(size_t a, size_t b, size_t c) * Return: number of bytes needed or SIZE_MAX on overflow. */ #define flex_array_size(p, member, count) \ - array_size(count, \ - sizeof(*(p)->member) + __must_be_array((p)->member)) + size_mul(count, \ + sizeof(*(p)->member) + __must_be_array((p)->member)) + +/** + * struct_size() - Calculate size of structure with trailing flexible array. + * + * @p: Pointer to the structure. + * @member: Name of the array member. + * @count: Number of elements in the array. + * + * Calculates size of memory needed for structure @p followed by an + * array of @count number of @member elements. + * + * Return: number of bytes needed or SIZE_MAX on overflow. + */ +#define struct_size(p, member, count) \ + size_add(sizeof(*(p)), flex_array_size(p, member, count))
#endif /* __LINUX_OVERFLOW_H */ diff --git a/lib/test_overflow.c b/lib/test_overflow.c index 7a4b6f6c5473..7a5a5738d2d2 100644 --- a/lib/test_overflow.c +++ b/lib/test_overflow.c @@ -588,12 +588,110 @@ static int __init test_overflow_allocation(void) return err; }
+struct __test_flex_array { + unsigned long flags; + size_t count; + unsigned long data[]; +}; + +static int __init test_overflow_size_helpers(void) +{ + struct __test_flex_array *obj; + int count = 0; + int err = 0; + int var; + +#define check_one_size_helper(expected, func, args...) ({ \ + bool __failure = false; \ + size_t _r; \ + \ + _r = func(args); \ + if (_r != (expected)) { \ + pr_warn("expected " #func "(" #args ") " \ + "to return %zu but got %zu instead\n", \ + (size_t)(expected), _r); \ + __failure = true; \ + } \ + count++; \ + __failure; \ +}) + + var = 4; + err |= check_one_size_helper(20, size_mul, var++, 5); + err |= check_one_size_helper(20, size_mul, 4, var++); + err |= check_one_size_helper(0, size_mul, 0, 3); + err |= check_one_size_helper(0, size_mul, 3, 0); + err |= check_one_size_helper(6, size_mul, 2, 3); + err |= check_one_size_helper(SIZE_MAX, size_mul, SIZE_MAX, 1); + err |= check_one_size_helper(SIZE_MAX, size_mul, SIZE_MAX, 3); + err |= check_one_size_helper(SIZE_MAX, size_mul, SIZE_MAX, -3); + + var = 4; + err |= check_one_size_helper(9, size_add, var++, 5); + err |= check_one_size_helper(9, size_add, 4, var++); + err |= check_one_size_helper(9, size_add, 9, 0); + err |= check_one_size_helper(9, size_add, 0, 9); + err |= check_one_size_helper(5, size_add, 2, 3); + err |= check_one_size_helper(SIZE_MAX, size_add, SIZE_MAX, 1); + err |= check_one_size_helper(SIZE_MAX, size_add, SIZE_MAX, 3); + err |= check_one_size_helper(SIZE_MAX, size_add, SIZE_MAX, -3); + + var = 4; + err |= check_one_size_helper(1, size_sub, var--, 3); + err |= check_one_size_helper(1, size_sub, 4, var--); + err |= check_one_size_helper(1, size_sub, 3, 2); + err |= check_one_size_helper(9, size_sub, 9, 0); + err |= check_one_size_helper(SIZE_MAX, size_sub, 9, -3); + err |= check_one_size_helper(SIZE_MAX, size_sub, 0, 9); + err |= check_one_size_helper(SIZE_MAX, size_sub, 2, 3); + err |= check_one_size_helper(SIZE_MAX, size_sub, SIZE_MAX, 0); + err |= check_one_size_helper(SIZE_MAX, size_sub, SIZE_MAX, 10); + err |= check_one_size_helper(SIZE_MAX, size_sub, 0, SIZE_MAX); + err |= check_one_size_helper(SIZE_MAX, size_sub, 14, SIZE_MAX); + err |= check_one_size_helper(SIZE_MAX - 2, size_sub, SIZE_MAX - 1, 1); + err |= check_one_size_helper(SIZE_MAX - 4, size_sub, SIZE_MAX - 1, 3); + err |= check_one_size_helper(1, size_sub, SIZE_MAX - 1, -3); + + var = 4; + err |= check_one_size_helper(4 * sizeof(*obj->data), + flex_array_size, obj, data, var++); + err |= check_one_size_helper(5 * sizeof(*obj->data), + flex_array_size, obj, data, var++); + err |= check_one_size_helper(0, flex_array_size, obj, data, 0); + err |= check_one_size_helper(sizeof(*obj->data), + flex_array_size, obj, data, 1); + err |= check_one_size_helper(7 * sizeof(*obj->data), + flex_array_size, obj, data, 7); + err |= check_one_size_helper(SIZE_MAX, + flex_array_size, obj, data, -1); + err |= check_one_size_helper(SIZE_MAX, + flex_array_size, obj, data, SIZE_MAX - 4); + + var = 4; + err |= check_one_size_helper(sizeof(*obj) + (4 * sizeof(*obj->data)), + struct_size, obj, data, var++); + err |= check_one_size_helper(sizeof(*obj) + (5 * sizeof(*obj->data)), + struct_size, obj, data, var++); + err |= check_one_size_helper(sizeof(*obj), struct_size, obj, data, 0); + err |= check_one_size_helper(sizeof(*obj) + sizeof(*obj->data), + struct_size, obj, data, 1); + err |= check_one_size_helper(SIZE_MAX, + struct_size, obj, data, -3); + err |= check_one_size_helper(SIZE_MAX, + struct_size, obj, data, SIZE_MAX - 3); + + pr_info("%d overflow size helper tests finished\n", count); + + return err; +} + static int __init test_module_init(void) { int err = 0;
err |= test_overflow_calculation(); err |= test_overflow_shift(); + err |= test_overflow_size_helpers(); err |= test_overflow_allocation();
if (err) {