kernel/linux.git/Documentation/process/deprecated.rst, branch v5.10.258

overflow: Implement size_t saturating arithmetic helpers

2023-11-20T10:06:44+00:00

[ 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 Cc: Gustavo A. R. Silva Cc: Nathan Chancellor Cc: Jason Gunthorpe Cc: Nick Desaulniers Cc: Leon Romanovsky Cc: Keith Busch Cc: Len Baker Signed-off-by: Kees Cook Stable-dep-of: d692873cbe86 ("gve: Use size_add() in call to struct_size()") Signed-off-by: Sasha Levin

docs: deprecated.rst: Expand str*cpy() replacement notes

2020-10-21T21:09:16+00:00

The notes on replacing the deprecated str*cpy() functions didn't call enough attention to the change in return type. Add these details and clean up the language a bit more. Signed-off-by: Kees Cook Acked-by: Gustavo A. R. Silva Link: https://lore.kernel.org/r/20201015231730.2138505-1-keescook@chromium.org Signed-off-by: Jonathan Corbet

docs: deprecated.rst: Update zero-length/one-element arrays section

2020-09-09T17:37:49+00:00

Update information in the zero-length and one-element arrays section and illustrate how to make use of the new flex_array_size() helper, together with struct_size() and a flexible-array member. Signed-off-by: Gustavo A. R. Silva Acked-by: Kees Cook Link: https://lore.kernel.org/r/20200901010949.GA21398@embeddedor Signed-off-by: Jonathan Corbet

deprecated.rst: Remove now removed uninitialized_var

2020-08-31T22:31:15+00:00

It's now gone from the kernel so remove it from the deprecated API text. Signed-off-by: Joe Perches Reviewed-by: Nick Desaulniers Link: https://lore.kernel.org/r/5e10c1645dd8f735215cf54a74db0f8dd3f6cbd5.camel@perches.com Signed-off-by: Jonathan Corbet

docs: Fix function name trailing double-()s

2020-08-24T23:19:07+00:00

I noticed a double-() in the deprecated.rst rendering today. Fix that one and two others in the Documentation/ tree. Acked-by: "Paul E. McKenney" # For RCU Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20200817233207.4083538-1-keescook@chromium.org Signed-off-by: Jonathan Corbet

Merge tag 'docs-5.9' of git://git.lwn.net/linux

2020-08-05T05:47:54+00:00

Pull documentation updates from Jonathan Corbet: "It's been a busy cycle for documentation - hopefully the busiest for a while to come. Changes include: - Some new Chinese translations - Progress on the battle against double words words and non-HTTPS URLs - Some block-mq documentation - More RST conversions from Mauro. At this point, that task is essentially complete, so we shouldn't see this kind of churn again for a while. Unless we decide to switch to asciidoc or something...:) - Lots of typo fixes, warning fixes, and more" * tag 'docs-5.9' of git://git.lwn.net/linux: (195 commits) scripts/kernel-doc: optionally treat warnings as errors docs: ia64: correct typo mailmap: add entry for doc/zh_CN: add cpu-load Chinese version Documentation/admin-guide: tainted-kernels: fix spelling mistake MAINTAINERS: adjust kprobes.rst entry to new location devices.txt: document rfkill allocation PCI: correct flag name docs: filesystems: vfs: correct flag name docs: filesystems: vfs: correct sync_mode flag names docs: path-lookup: markup fixes for emphasis docs: path-lookup: more markup fixes docs: path-lookup: fix HTML entity mojibake CREDITS: Replace HTTP links with HTTPS ones docs: process: Add an example for creating a fixes tag doc/zh_CN: add Chinese translation prefer section doc/zh_CN: add clearing-warn-once Chinese version doc/zh_CN: add admin-guide index doc:it_IT: process: coding-style.rst: Correct __maybe_unused compiler label futex: MAINTAINERS: Re-add selftests directory ...

docs: deprecated.rst: Add uninitialized_var()

2020-07-16T19:32:24+00:00

Nothing should be using this macro, and the entire idea of tricking the compiler into silencing such warnings is a mistake. Cc: Jonathan Corbet Cc: "Gustavo A. R. Silva" Cc: Joe Perches Cc: linux-doc@vger.kernel.org Reviewed-by: Nick Desaulniers Signed-off-by: Kees Cook

docs: deprecated.rst: Add zero-length and one-element arrays

2020-06-19T19:39:01+00:00

Add zero-length and one-element arrays to the list. While I continue replacing zero-length and one-element arrays with flexible-array members, I need a reference to point people to, so they don't introduce more instances of such arrays. And while here, add a note to the "open-coded arithmetic in allocator arguments" section, on the use of struct_size() and the arrays-to-deprecate mentioned here. Co-developed-by: Kees Cook Signed-off-by: Kees Cook Signed-off-by: Gustavo A. R. Silva Acked-by: Kees Cook Link: https://lore.kernel.org/r/20200608213711.GA22271@embeddedor Signed-off-by: Jonathan Corbet

docs: deprecated.rst: Add BUG()-family

2020-03-20T23:24:49+00:00

Linus continues to remind[1] people to stop using the BUG()-family of functions. We should have this better documented (even if checkpatch.pl has been warning[2] since 2015), so add more details to deprecated.rst, as a distinct place to point people to for guidance. [1] https://lore.kernel.org/lkml/CAHk-=whDHsbK3HTOpTF=ue_o04onRwTEaK_ZoJp_fjbqq4+=Jw@mail.gmail.com/ [2] https://git.kernel.org/linus/9d3e3c705eb395528fd8f17208c87581b134da48 Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/202003141524.59C619B51A@keescook Signed-off-by: Jonathan Corbet

docs: Remove :c:func: from process/deprecated.rst

2020-03-10T17:27:22+00:00

Documentation/process/deprecated.rst has a lot of uses of :c:func:, which is, well, deprecated. Emacs query-replace-regexp to the rescue. Signed-off-by: Jonathan Corbet