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e1be43d9b5
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>
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| .. | ||
| 1.Intro.rst | ||
| 2.Process.rst | ||
| 3.Early-stage.rst | ||
| 4.Coding.rst | ||
| 5.Posting.rst | ||
| 6.Followthrough.rst | ||
| 7.AdvancedTopics.rst | ||
| 8.Conclusion.rst | ||
| adding-syscalls.rst | ||
| applying-patches.rst | ||
| botching-up-ioctls.rst | ||
| changes.rst | ||
| clang-format.rst | ||
| code-of-conduct-interpretation.rst | ||
| code-of-conduct.rst | ||
| coding-style.rst | ||
| deprecated.rst | ||
| development-process.rst | ||
| email-clients.rst | ||
| embargoed-hardware-issues.rst | ||
| howto.rst | ||
| index.rst | ||
| kernel-docs.rst | ||
| kernel-driver-statement.rst | ||
| kernel-enforcement-statement.rst | ||
| license-rules.rst | ||
| magic-number.rst | ||
| maintainer-handbooks.rst | ||
| maintainer-pgp-guide.rst | ||
| maintainer-tip.rst | ||
| maintainers.rst | ||
| management-style.rst | ||
| programming-language.rst | ||
| stable-api-nonsense.rst | ||
| stable-kernel-rules.rst | ||
| submit-checklist.rst | ||
| submitting-drivers.rst | ||
| submitting-patches.rst | ||
| volatile-considered-harmful.rst | ||