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[ Upstream commite1be43d9b5] 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:e001e60869("fs/ntfs3: Harden against integer overflows") Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.