kernel/linux.git/include/linux/overflow.h, branch v6.19.11

overflow: Introduce struct_offset() to get offset of member

2025-11-28T01:18:05+00:00

The trace_marker_raw file in tracefs takes a buffer from user space that contains an id as well as a raw data string which is usually a binary structure. The structure used has the following: struct raw_data_entry { struct trace_entry ent; unsigned int id; char buf[]; }; Since the passed in "cnt" variable is both the size of buf as well as the size of id, the code to allocate the location on the ring buffer had: size = struct_size(entry, buf, cnt - sizeof(entry->id)); Which is quite ugly and hard to understand. Instead, add a helper macro called struct_offset() which then changes the above to a simple and easy to understand: size = struct_offset(entry, id) + cnt; This will likely come in handy for other use cases too. Link: https://lore.kernel.org/all/CAHk-=whYZVoEdfO1PmtbirPdBMTV9Nxt9f09CK0k6S+HJD3Zmg@mail.gmail.com/ Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: "Gustavo A. R. Silva" Link: https://patch.msgid.link/20251126145249.05b1770a@gandalf.local.home Suggested-by: Linus Torvalds Reviewed-by: Kees Cook Signed-off-by: Steven Rostedt (Google)

overflow: add range_overflows() and range_end_overflows()

2025-09-08T12:36:19+00:00

Move the range_overflows() and range_end_overflows() along with the _t variants over from drm/i915 and drm/buddy to overflow.h. Cc: Kees Cook Cc: "Gustavo A. R. Silva" Cc: linux-hardening@vger.kernel.org Reviewed-by: Kees Cook Reviewed-by: Jouni Högander Acked-by: Thomas Zimmermann Link: https://lore.kernel.org/r/20250829174601.2163064-3-jani.nikula@intel.com Signed-off-by: Jani Nikula

overflow: Introduce __DEFINE_FLEX for having no initializer

2025-06-01T15:41:11+00:00

While not yet in the tree, there is a proposed patch[1] that was depending on the prior behavior of _DEFINE_FLEX, which did not have an explicit initializer. Provide this via __DEFINE_FLEX now, which can also have attributes applied (e.g. __uninitialized). Examples of the resulting initializer behaviors can be seen here: https://godbolt.org/z/P7Go8Tr33 Link: https://lore.kernel.org/netdev/20250520205920.2134829-9-anthony.l.nguyen@intel.com [1] Fixes: 47e36ed78406 ("overflow: Fix direct struct member initialization in _DEFINE_FLEX()") Signed-off-by: Kees Cook

overflow: Fix direct struct member initialization in _DEFINE_FLEX()

2025-05-08T16:42:05+00:00

Currently, to statically initialize the struct members of the `type` object created by _DEFINE_FLEX(), the internal `obj` member must be explicitly referenced at the call site. See: struct flex { int a; int b; struct foo flex_array[]; }; _DEFINE_FLEX(struct flex, instance, flex_array, FIXED_SIZE, = { .obj = { .a = 0, .b = 1, }, }); This leaks _DEFINE_FLEX() internal implementation details and make the helper harder to use and read. Fix this and allow for a more natural and intuitive C99 init-style: _DEFINE_FLEX(struct flex, instance, flex_array, FIXED_SIZE, = { .a = 0, .b = 1, }); Note that before these changes, the `initializer` argument was optional, but now it's required. Also, update "counter" member initialization in DEFINE_FLEX(). Fixes: 26dd68d293fd ("overflow: add DEFINE_FLEX() for on-stack allocs") Signed-off-by: Gustavo A. R. Silva Link: https://lore.kernel.org/r/aBQVeyKfLOkO9Yss@kspp Signed-off-by: Kees Cook

overflow: Add STACK_FLEX_ARRAY_SIZE() helper

2025-05-08T16:42:05+00:00

Add new STACK_FLEX_ARRAY_SIZE() helper to get the size of a flexible-array member defined using DEFINE_FLEX()/DEFINE_RAW_FLEX() at compile time. This is essentially the same as ARRAY_SIZE() but for on-stack flexible-array members. Signed-off-by: Gustavo A. R. Silva Link: https://lore.kernel.org/r/83d53744e11c80eb3f03765238cbe648855f4168.1745355442.git.gustavoars@kernel.org Signed-off-by: Kees Cook

overflow: Clarify expectations for getting DEFINE_FLEX variable sizes

2025-04-28T17:32:43+00:00

Mention the use of __member_size() for DEFINE_FLEX variables as a hint for getting at the compile-time size of the resulting flexible array member. Reviewed-by: Gustavo A. R. Silva Link: https://lore.kernel.org/r/20250416172911.work.854-kees@kernel.org Signed-off-by: Kees Cook

overflow: Change DEFINE_FLEX to take __counted_by member

2024-03-22T23:25:31+00:00

The norm should be flexible array structures with __counted_by annotations, so DEFINE_FLEX() is updated to expect that. Rename the non-annotated version to DEFINE_RAW_FLEX(), and update the few existing users. Additionally add selftests for the macros. Reviewed-by: Gustavo A. R. Silva Link: https://lore.kernel.org/r/20240306235128.it.933-kees@kernel.org Reviewed-by: Przemek Kitszel Signed-off-by: Kees Cook

overflow: Allow non-type arg to type_max() and type_min()

2024-03-02T00:03:32+00:00

A common use of type_max() is to find the max for the type of a variable. Using the pattern type_max(typeof(var)) is needlessly verbose. Instead, since typeof(type) == type we can just explicitly call typeof() on the argument to type_max() and type_min(). Add wrappers for readability. We can do some replacements right away: $ git grep '\btype_$min\|max$(typeof' | wc -l 11 Link: https://lore.kernel.org/r/20240301062221.work.840-kees@kernel.org Signed-off-by: Kees Cook

overflow: Use POD in check_shl_overflow()

2024-02-29T21:38:03+00:00

The check_shl_overflow() uses u64 type that is defined in types.h. Instead of including that header, just switch to use POD type directly. Signed-off-by: Andy Shevchenko Acked-by: Kees Cook Link: https://lore.kernel.org/r/20240228204919.3680786-2-andriy.shevchenko@linux.intel.com Signed-off-by: Kees Cook

overflow: Introduce wrapping_assign_add() and wrapping_assign_sub()

2024-02-29T21:38:01+00:00

This allows replacements of the idioms "var += offset" and "var -= offset" with the wrapping_assign_add() and wrapping_assign_sub() helpers respectively. They will avoid wrap-around sanitizer instrumentation. Add to the selftests to validate behavior and lack of side-effects. Reviewed-by: Marco Elver Acked-by: Mark Rutland Signed-off-by: Kees Cook