Flexible Array Transformations and Array-bounds Checking
summary
Kernel code is being converted from one-element and zero-length trailing arrays into C99 flexible-array members so compilers and fortified memcpy can actually reason about sizes; transforming zero-length arrays is mostly done but one-element conversions need manual audit for off-by-one bugs and ABI-safe UAPI handling using the declare_flex_array helper. GCC currently treats all trailing arrays as flexible so __builtin_object_size returns -1; a new option -fstrict-flex-arrays (levels up to true-only) plus use of struct_size and tools like objdump and Ghidra are needed to finish enabling -Warray-bounds and hardened memcpy.
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chapters (4)
- 0:00Start
- 12:15Problems with ambiguous flexible-array variants
- 34:28The case of UAPI
- 36:19Flexible array transformations in the Linux kernel
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