I believe only Ubuntu is affected, of the major distros. The bug affects kernels compiled with CONFIG_X86_X32, which enables the new-ish x32 ABI, a way for proc

I believe only Ubuntu is affected, of the major distros. The bug affects kernels compiled with CONFIG_X86_X32, which enables the new-ish x32 ABI, a way for processes to use x86-64 features like the extended register set, while retaining the 32-bit pointer size. The more conventional approach to 32/64-bit code mixing (e.g. in Debian) is that 32-bit processes use the old x86 ABI, while 64-bit processes use the new x86-64 ABI. The x32 ABI was borne out of people noticing that the x86-64 architecture's improvements weren't all about 64-bitness, and that some of them were relevant to 32-bit programs too. So it keeps 32-bit pointers, but otherwise uses x86-64 features, so even 32-bit processes can take advantage of running on x86-64 chips (everything except the 64-bit part). Nothing inherently wrong with the idea, but it introduces some new critical codepaths into the kernel that have to be thoroughly tested.