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overflow: Implement size_t saturating arithmetic helpers

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[ 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: d692873cbe86 ("gve: Use size_add() in call to struct_size()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kees Cook
2021-09-18 15:17:53 -07:00
committed by Greg Kroah-Hartman
parent 2f4b4eb58f
commit 2b46db3bb7
3 changed files with 197 additions and 57 deletions
Download Patch File Download Diff File Expand all files Collapse all files

98
lib/test_overflow.c
View File

@@ -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) {